This PDF file contains the front matter associated with SPIE Proceedings Volume 7298, including the Title Page, Copyright information, Table of Contents, Introduction(if any), and the Conference Committee listing.

An airborne thermal hyperspectral imager is underdevelopment which utilizes the compact Dyson optical configuration and quantum well infrared photo detector (QWIP) focal plane array. The Dyson configuration uses a single monolithic prism-like grating design which allows for a high throughput instrument (F/1.6) with minimal ghosting, stray-light and large swath width. The configuration has the potential to be the optimal imaging spectroscopy solution unmanned aerial vehicles (UAV) due to its small form factor and relatively low power requirements. The planned instrument specifications are discussed as well as design trade-offs. Calibration testing results (noise equivalent temperature difference, spectral linearity and spectral bandwidth) and laboratory emissivity plots from samples are shown using an operational testbed unit which has similar specifications as the final airborne system. Field testing of the testbed unit was performed to acquire plots of emissivity for various known standard minerals (quartz). A comparison is made using data from the ASTER spectral library.

Concentric spectrometer forms are advantageous for constructing a variety of systems spanning the entire visible to infrared range. Spectrometer examples are given, including broadband or high resolution forms. Some issues associated with the Dyson catadioptric type are also discussed.

We have demonstrated the use of bulk antimonide based materials and type-II antimonide based superlattices in the development of large area mid wavelength infrared (MWIR) focal plane arrays (FPAs) as well as smaller format long wavelength infrared (LWIR) arrays. Barrier infrared photodetectors (BIRDs) and superlattice-based infrared photodetectors are expected to outperform traditional III-V MWIR and LWIR imaging technologies and are expected to offer significant advantages over II-VI material based FPAs. We have used molecular beam epitaxy (MBE) technology to grow InAs/GaSb superlattice pin photodiode and bulk InAsSb structures on GaSb substrates. The coupled quantum well superlattice device offers additional control in wavelength tuning via quantum well sizes and ternary composition. Furthermore, we have fabricated mid-wavelength 1024x1024 pixels superlattice imaging FPAs, 640x512 MWIR arrays based on the BIRD concept, and 256x256 LWIR arrays based on pin superlattice structures. These initial FPA have produced excellent infrared imagery.

We report work on several quantum structure based infrared detectors. We describe the concept and experimental progress of the quantum well intra-subband photodetector (QWISP), which is closely related to the quantum-well infrared photodetector (QWIP), but uses the dopant-assisted intra-subband absorption mechanism in quantum wells for normal-incidence far infrared/terahertz radiation detection. We describe the concept of the submonolayer quantum dot infrared photodetector (SML QDIP), and report experimental device results on long-wavelength infrared detection, and imaging results from a mega-pixel focal plane arrays, which produced clear infrared images up to 80K. We discuss how superlattice heterostructures, particularly those using unipolar barriers, can offer significant performance advantages over homojunction superlattices in infrared detection. We also summary recent device results on a superlattice heterostructure based barrier infrared detectors (BIRDs).

Mid-wave infrared (MWIR) and long-wave infrared (LWIR) multicolor focal plane array (FPA) cameras are essential for many DoD and NASA applications including Earth and planetary remote sensing. In this paper we summarize our recent development of large format multicolor QWIP FPA that cover MWIR and LWIR bands.

We are developing corrugated quantum well infrared photodetector (C-QWIP) technology for long wavelength applications. A number of large format 1024 × 1024 C-QWIP focal plane arrays (FPAs) have been demonstrated. The measured quantum efficiency η is ranging from 15 - 37%, depending on the detector type, doping density and number of quantum wells in the detector material. The photoconductive gain is between 0.07 and 0.19, while the spectral width is between 1.5 and 3.5 microns. Despite the large integrated η of the C-QWIPs, the number of collected photoelectrons can be limited in shorter cutoff, small pixel FPAs under high speed operation. In this case, the read noise will have a large impact on the system sensitivity. In this paper, we will discuss the detector model, the measured pixel characteristics, and the effects of read noise on the FPA performance. Our analysis shows that the tolerable read noise improves with the cutoff wavelength. For example, to achieve a sensitivity of 20 mK at 2 msec integration time, the respective read noise will be 1000, 2000, 3000, and 4000 e¯ at λ_c = 8.8, 9.4, 10.7 and 11.7 μm. This analysis will help to determine the read noise requirement for the C-QWIP FPAs.

μWe report the demonstration of multi-spectral quantum dots-in-a-well infrared photo-detectors through the coupling of incident light to resonant modes of surface plasmons. The integration of a surface plasmon assisted cavity with the detector results in shifting the peak wavelength of absorption of the detector to that of the resonant wavelength of the cavity. The cavity consists of a square lattice structure with square holes in it. A wavelength tuning of 8.5 to 9 μm was observed, by changing the pitch of the fabricated pattern forming the cavity. Polarization sensitive detectors can be fabricated by breaking the symmetry of the lattice. This is achieved by stretching the lattice constants along the x and y directions. A DWELL detector with resonant frequency at 6.8 μm where the response of the 0 ° polarization is twice as strong as the 90° polarization is reported. This technique, in principle, is detector agnostic and shows promise in fabrication of multi-spectral focal plane arrays (FPA).

We propose a new smart photodetector with adaptive multi-spectral polarization sensing and signal processing capabilities. The smart photodetector consists of a voltage-tunable multi-spectral polarimetric quantum dot infrared photodetector and high-speed (>5.6GHz) flexible electronics printed on the QDIP. Such integrated photodetection and on-chip processing would not only greatly enhance the detectors functionalities, but also substantially reduce the time delay by performing image processing locally.

The aim of this paper is to describe the results of various trials involving a high-resolution thermal imager that has been designed to be sensitive to polarised radiation. Polarisation has the potential to discriminate man-made objects and disturbed earth from background clutter. Polarisation combined with conventional thermal imaging within the one camera offers the potential to significantly reduce false alarms in surveillance and detection applications. The camera used during the trials is a technology demonstrator developed by Thales Optronics, UK. The camera operates in the longwave infra red and has a QWIP polarisation-sensitive detector. The results presented in this paper include recent trials in the UK and USA. The aim of the trials was to assess the utility in using a LWIR polarimeter for detection of difficult objects from background clutter. Thermal and polarised images were captured and processed in order to detect anomalies. Several polarisation-based discriminative imaging techniques are applied to trials imagery. The effect of the diurnal cycle on the effectiveness of polarisation for object discrimination will be assessed.

This work demonstrates the use of the Transfer Matrix Method (TMM) to calculate the band structure of complex heterostructures in both valence and conduction band. The method shows versatility in obtaining the transmission coefficient, the energy states and the corresponding wave functions of a structure comprised of a large number of semiconductor layers. This ability is essential in Quantum Wells Infrared Photodetectors (QWIP) design using interband and intersubband transitions. To implement that, selected Hamiltonians are solved separately for conduction and valence bands. The method is validated comparing numerical results with analytical solutions of potentials such as Modified Posch-Teller. Furthermore, several results from the literature were reproduced by the TMM showing good agreement, with errors smaller than 5%. Finally, the method is used to estimate the responsivity wavelength peak of a QWIP using interband and intersubband transitions to detect near-, mid- and long infrared (NWIR, MWIR, LWIR). The comparison between measurements and the simulation showed good agreement, with an average error smaller than 3% for both interband and intersubband transitions. Those results indicate that the TMM is a suitable method to be used in QWIP design.

We report a very longwave Infrared (> 14 μm) quantum dot photodetector working at 77 K. Very longwave infrared (VLWIR) detection at a cut-off wavelength of 15.3 μm was achieved through QD size engineering. Peak specific photodetectivity D* of 3.3x10⁸ cmHz^1/2/W. A large photoresponsivity of 0.93 A/W and high photoconductive gain of 62.4 were demonstrated at a bias voltage of V = 3.7 V at T = 77 K. The low-bias and liquid nitrogen temperature performance demonstration based on InAs-GaAs material systems indicates that the QDIP technology is promising for VLWIR sensing and imaging.

Recently, quantum dot infrared photodetectors (QDIP) have been intensively investigated because they can be fabricated by conventional matured GaAs processing. QDIP can detect normal incident light in contrast to quantum well infrared photodetectors (QWIP) which need optical grating or reflector. Also QDIPs operate at higher temperature, taking advantage of their lower dark current theoretically than that of QWIPs. In this report, we describe our effort to realize long-wavelength infrared (LWIR) QDIP infrared focal plane array (IRFPA), which uses molecular beam epitaxially grown self-assembled quantum dot (SAQD) multilayers. We have successfully "engineered" the transition levels of SAQDs to LWIR (8-12 μm) energy region, where relatively lower quantum levels were pushed up near the conduction band edge of AlGaAs intermediate layers. In addition, these SAQD multilayers bring QDIP responsivity enhancement due to their higher dot density. We applied this structure to 256×256 pixel LWIR QDIP IRFPA. As a result, we realized the response peak wavelength of 10 μm and noise equivalent temperature difference of our newly developed QDIP was 87 mK at 80 K, 120 Hz frame rate with f/2.5 optics. We obtained the excellent quality of IR image and confirmed our QDIP's high sensitivity and high speed operation.

Historically IRnova has exclusively been a company, focused on manufacturing of QWIP detectors. Nowadays, besides continuous improvements of the performance of QWIP FPAs and development of new formats IRnova is involved in development of QWIP detectors for special applications and has started the development of the next generation infrared detectors, as well. In the light of the development of new formats we validate experimentally theoretical calculations of the response of QWIPs for smaller pixel size. These results allow for the development of high performance megapixel QWIP FPA that exhibit the high uniformity and operability QWIP detectors are known for. QWIP is also being considered for space applications. The requirements on dark current and operating temperature are however much more stringent as compared to the terrestrial applications. We show ways to improve the material quality with as a result a higher detector operating temperature. IRnova is also looking at antimony-based strained superlattice material for the LWIR region together with partners at the IMAGIC centre of excellence. One of the ways to overcome the problem with surface currents is passivating overgrowth. We will report the status and results of overgrowing the detector mesas with AlGa(As)Sb in a MOVPE system. At the same centre of excellence a novel material concept is being developed for LWIR detection. This new material contains a superlattice of vertically aligned and electronically coupled InAs and GaSb quantum dots. Simulations show that it should be possible to have LWIR detection in this material. We will present the current status and report results in this research.

Since 2002, the THALES Group has been manufacturing sensitive arrays using QWIP technology based on GaAs and related III-V compounds, at the Alcatel-Thales-III-V Lab (formerly part of THALES Research and Technology Laboratory). In the past researchers claimed many advantages of QWIPs. Uniformity was one of these and has been the key parameter for the production to start. Another widely claimed advantage for QWIPs was the so-called band-gap engineering and versatility of the III-V processing allowing the custom design of quantum structures at various wavelengths in MWIR, LWIR and VLWIR. An overview of the available performances of QWIPs in the whole infrared spectrum is presented here. We also discuss about the under-development products such as dual band and polarimetric structures.

Detectors composed of novel Antimonide Based Compound Semiconductor (ABCS) materials offer some unique advantages. InAs/GaSb type II superlattices (T2SL) offer low dark currents and allow full bandgap tunability from the MWIR to the VLWIR. InAs_1-xSb_x alloys (x~0.1) also offer low dark currents and can be used to make MWIR devices with a cut-off wavelength close to 4.2μm. Both can be grown on commercially available GaSb substrates and both can be combined with lattice matched GaAlSbAs barrier layers to make a new type of High Operating Temperature (HOT) detector, known as an XBn detector. In an XBn detector the Generation-Recombination (G-R) contribution to the dark current can be suppressed, giving a lower net dark current, or allowing the same dark current to be reached at a higher temperature than in a conventional photodiode. The ABCS program at SCD began several years ago with the development of an epi-InSb detector whose dark current is about 15 times lower than in standard implanted devices. This detector is now entering production. More recently we have begun developing infrared detectors based both on T2SL and InAsSb alloy materials. Our conventional photodiodes made from T2SL materials with a cut-off wavelength in the region of 4.6μm exhibit dark currents consistent with a BLIP temperature of ~ 120-130K at f/3. Characterization results of the T2SL materials and diodes are presented. We have also initiated a program to validate the XBn concept and to develop high operating temperature InAsSb XBn detectors. The crystallographic, electrical and optical properties of the XBn materials and devices are discussed. We demonstrate a BLIP temperature of ~ 150K at f/3.

Novel thermo-mechanical detector arrays with integrated diffraction grating for optical readout were designed and fabricated. Parylene was used as the structural material due to its high thermal isolation and mismatch properties. Calculations reveal that the NETD performance of a thermo-mechanical array using Parylene can be significantly better than SiNx based designs and offer a theoretical NETD value <10mK assuming an optical readout with a high dynamic range detector array. Finite Element simulations were performed with length of the bimaterial leg as the optimization parameter. It was observed that only a few microns of isolation leg supported 30 fps applications, leaving rest of the leg to be bimaterial and providing large thermo-mechanical deflections.

In an optical-readout photomechanical imager, the infrared sensor array is physically separated from the ROIC. The modularity of the optical readout architecture allows for extra design freedom that is not possible in bolometers, negating fundamental trade-offs, such as NETD versus thermal time constant. For successful commercialization, the photomechanical imager must meet application-specific performance and functional targets, and to this end, Agiltron has advanced the photomechanical imaging platform over several technology generations. Improvements have been made to both the optical readout system and the photomechanical sensor chip, which enabled reductions in size, weight, and power (SWAP) and NETD over successive generations. The current-generation photomechanical imager has the size equivalent to a digital camera and an ƒ/1-equivalent NETD and MDTD of less than 100 mK.

The introduction of an uncooled microbolometer image sensor about a decade ago enabled cost reduction of IR cameras. As a result, the available markets grew both in military and civilian applications. Since then, the price of microbolometer was gradually reduced due to introduction of devices with smaller pixel, maturity of the technology and quantity growth. However, the requirement for a vacuum package still limits the price of microbolometer based cameras to several thousands of dollars. Sirica's novel wavelength conversion technology aims at breaking this paradigm by being uncooled and vacuumless, lowering IR camera prices by an order of magnitude, opening the way to new mass markets. Sirica's proprietary IR-to-Visible/NIR conversion layer allows for low-cost high performance LWIR detector with no requirement for cooling and vacuum packaging. In the last years, the development efforts focused on development of the conversion media. Recently, a parallel effort for the integration of the conversion layer together with other detector components has started. Packaging of detector components, such as conversion layer, pumping light source, dichroic filter, and their coupling with silicon CMOS image sensor have great importance from a price-performance point of view. According to the company's business-development roadmap, the detector prototype should be available during the first quarter of 2010.

Thin film Si_xGe_1-xO_y infrared sensitive material was grown by RF magnetron sputtering, by depositing Si and Ge thin film simultaneously from two deposition targets in an oxygen (O) and argon environment at room temperature and at 400°C. Film composition was varied by adjusting RF power applied to the silicon target and by varying the oxygen flow of the gas mixture in the deposition chamber. The atomic compositions of Si, Ge, and O in the deposited thin film were determined and analyzed using energy dispersive X-ray spectroscopy (EDS). The influence of changing Ge and Si and O compositions on temperature coefficient of resistance (TCR), and resistivity were studied. Different fabrication scenarios have been used to vary the Ge, Si and O concentrations. The highest achieved TCRs and the corresponding resistivities at room temperature were -4.86 %/K and -6.43 %/K, and 2.45×10² Ω cm and 3.34×10² Ω cm using Si_0.195Ge_0.706O_0.099and Si_0.127Ge_0.835O_0.038 for films deposited at room temperature and at 400 ^oC, respectively.

The use of a cross-shaped patterned resistive sheet as an infrared-selective absorber, including the effects of a SiNx mechanical support dielectric layer is discussed. These cross patterned resistive sheets are a modified form of classical Salisbury Screens that utilize a resistive absorber layer placed a quarter-wavelength in front of a mirror. In comparison with previously designed patterned resistive sheets that have only a single resistive layer with rectangular patterned holes, here we consider a resistive absorber layer and a support dielectric layer with cross patterned holes through both the resistive absorption layer and the support layer.

A MEMS-less infrared pyroelectric sensor that employs an active detection mechanism based on a strontium bismuth tantalate (SrBi₂Ta₂O₉) ferroelectric sensing material is described and compared to passive modes of operation. A model is based on fundamental performance of ferroelectrics in which the polarization state of the material is actively interrogated enabling improved signal to noise ratio, greater effective pyroelectric coefficient, and chopper-less design. In addition to excellent thermal responsivity in the medium and long wavelength bands and unlimited endurance, the unique design enables selective wavelength tuning of insulating layer and absorber materials to maximize the responsivity at distinct wavelengths.

This paper presents an 80 x 60 element thermoelectric infrared focal plane array that provides high responsivity and a low cost/high volume potential. The device has been designed to have a responsivity of 2100 V/W. The overall chip size is 12.2mm x 9.3mm with a 10.4mm x 7.8mm imaging area. Each detector consists of three pairs of p-n polysilicon thermocouples with external dimensions of 130um x 130um and an internal resistance of 90k ohms. The thermal time constant for this device is ≈ 16ms. Compatible with standard CMOS processes this bulk micromachined focal plane array delivers near microbolometer performance making very low cost infrared cameras economically feasible.

This study represents an investigation of the feasibility of thin nickel oxide film (~100nm in thickness) as a microbolometer material. Thin nickel oxide film was obtained by a heat treatment (below 400 °C) of DC-sputtered Ni film on a SiO2/Si substrate in an O2 environment. Using a parameter analyzer (4156A) with a TEC temperature controller, a spectrum analyzer and a low noise amplifier, a systemic analysis of the electrical and noise characteristics of nickel oxide film is performed. A negative temperature coefficient of resistance (TCR) value of 3.28%/oC and a feasible 1/f noise result ranging from 1Hz to 100Hz were acquired. The characteristics of the thin nickel oxide film obtained in this study are comparable to those of a-Si. Moreover, the nickel oxide thin film retained a stable state at room temperature. Thus, the thin nickel oxide, which is CMOS-compatible and yields high TCR values and proper 1/f noise characteristics through a simple fabrication process, is shown to be a promising micro-bolometric material.

BAE Systems has continued to advance its 17 μm pitch LWIR 640 x 480 microbolometer technology with improvements in pixel performance and initial production for several emerging products. In addition, we have developed short time constant variants of our standard pixel design to support applications requiring short thermal time constants. The technology is expanding to include a 1024x768 format megapixel FPA to support higher resolution applications.

The high level of accumulated expertise by ULIS and CEA/LETI on uncooled microbolometers made from amorphous silicon enables ULIS to develop 1024 x 768 (XGA) IRFPA formats with 17μm pixel-pitch to address high end, high performance applications. This detector has kept all the innovations developed on the full TV format readout integrated circuit (ROIC): detector configuration by serial link, two video outputs, low power consumption, wide electrical dynamic range... The specific appeal of this unit lies in the high image resolution it provides. The reduction of the pixel-pitch turns this XGA array into a product well adapted for high resolution yet compact systems. In the last part of the paper, we will look more closely at the high electro-optical performances of this IRFPA and the rapid performance enhancement. We will insist on NETD coupled with wide thermal dynamic range, as well as the outstanding uniformity and high pixel operability, achieved thanks to the mastering of the amorphous silicon technology coupled with the ROIC design. This technology node paves the way to high end VGA or 1/4VGA sensors as well as large diffusion compact smaller formats like 160 x 120 or smaller.

In this paper SCD's 17μm pitch large format VOx μ-Bolometer detector is introduced. In the first part the radiometric performance and the challenges involved in achieving the desired pixel sensitivity are discussed. We elaborate on the progress towards the performance design goal (< 50mK@F/1, 60Hz) utilizing various test structures and technology demonstration platforms. The combination of reduced pixel size and high-end thermal sensitivity can provide smaller light weight systems. In the second part the ROIC architecture options will be presented in depth. New capabilities and features are enabled by the advanced 0.18um VLSI technology. Explicitly, we address the contribution in terms of system flexibility, simplification and reduced power dissipation. Some vital tasks, such as coarse non-uniformity correction, are done internally thus facilitating the user interface.

This paper provides an update of 17 micron pixel pitch uncooled microbolometer development at DRS. Since the introduction of 17 micron pitch 640x480 focal plane arrays (FPAs) in 2006, significant progress has been made in sensor performance and manufacturing processes. The FPAs are now in initial production with an FPA noise equivalent temperature difference (NETD), detector thermal time constant, and pixel operability equivalent or better than that of the current 25 micron pixel pitch production FPAs. NETD improvement was achieved without compromising detector thermal response or thermal time constant by simultaneous reduction in bolometer heat capacity and thermal conductance. In addition, the DRS unique "umbrella" microbolometer cavities were optically tuned to optimize detector radiation absorption for specific spectral band applications. The 17 micron pixel pitch FPAs are currently being considered for the next generation soldier systems such as thermal weapon sights (TWS), vehicle driver vision enhancers (DVE), digitally fused enhanced night vision goggles (DENVG) and unmanned air vehicle (UAV) surveillance sensors, because of overall thermal imaging system size, weight and power advantages.

Continued reduction of α-Si bolometer pixel size has led to increases in array size as well as improvements in temporal response for a given level of sensitivity. Programs funded by DARPA and NVESD are developing advanced 320×240, 640×480 and 1024×768 α-Si bolometer arrays with 17μm pixels, on-chip A/D conversion, significant improvements in dynamic range, significant reductions in thermal time constant and other specialized functions. The push to 17μm is motivated not only by system size and weight, but also by improvements in performance resulting from increased resolution. Smaller pixels permit fabrication of larger arrays without subverting the field-size constraints of ordinary photolithographic processes. Reducing pixel size also reduces the effects of stress mismatches. This permits reduction of device thickness, thereby reducing thermal time constant. Improvements in bolometer material properties have served to improve responsivity while lowering 1/f noise. Because these arrays substantially reduce sensor size, they are becoming the preferred format for most applications, particularly for weapon sights and for head-mounted and UAV applications. The larger array sizes are of interest for pilotage and surveillance.

In this paper we are presenting the ELOP concept of the night vision for the modern soldier. According to this concept the modern soldier's missions are divided into 4 main layers - situation awareness, improved lethality capabilities, target acquisition and surveillance. Based on this concept during the last few years ELOP has developed a family of products for those needs. Those new products are mainly based on the uncooled technology (with one exception). The uncooled technology allows cost eective solution with superior performance in comparison with image intensiers systems (by means of better robustness to poor lighting conditions, better immunity to dazzling etc.). Those products include thermal monocular, driver thermal sight, thermal weapon sights and hand held thermal cameras.

We have developed a novel readout circuit architecture realizing a TEC-less (Thermo-Electric Cooler) operation for an SOI diode uncooled infrared focal plane array (IRFPA). Through the fabrication of an SOI diode uncooled 320 x 240 IRFPA adopting the readout circuit architecture with our existing 25μm pixel-pitch technology, we demonstrate that the variation of the output DC level of the pixels is successfully suppressed in environmental temperatures from -10°C to 50°C. The developed TEC-less technology greatly enhances the ability of the SOI diode uncooled IRFPA, which inherently possesses excellent uniformity and low noise features.

We have developed a 32 μm pitch and 160 × 120 pixel uncooled infrared radiation focal plane array (IRFPA) on SOI by 0.35 μm CMOS technology and bulk-micromachining. For IR detection, we use silicon single crystal series p-n junctions which can realize high uniformity of temperature coefficient and low voltage drift. We have also developed a low-noise CMOS readout circuit on the same SOI which can calibrate the substrate temperature variation in every frame period, comparing two types of pixels, a bulk-micromachined infrared detection pixel and a non-micromachined reference pixel. Then the FPA requires no thermo-electric cooler (TEC) and is mounted on a low-cost standard ceramic package for the consumer products market.

In previous presentations to this SPIE forum a new technology was outlined aimed at replacing pyroelectric sensors with resistance microbolometer MOEMS-based sensors capable of vastly superior performance. The technology can be implemented as either a PCB replacement to current sensors, giving extended detection range and ability to sense slow temperature change, or a 'smart' sensor with further performance enhancements and imaging capability. This paper reports the results of new laboratory and field tests of a laboratory prototype sensor and extrapolates these results to performance of production sensors. In particular, results are presented for NETD, detection range for human targets and detection of simulated electrical faults and developing fires. Previous results were reported for FPA operated without evacuation and using a low cost plastic Fresnel lens. However with wafer level packaging now becoming widely available in MEMS and CMOS foundries, much high performance can be achieved, opening up many additional applications. Performance of new FPAs designed for vacuum packaging is highlighted.

The proliferation of security and surveillance missions in urban environments dictates the greater use of optical systems in situational awareness for ground vehicle protection. The need for total situation awareness requires unique optical based systems combining visible and thermal imaging, advanced image processing, and analytic functionalities. These sensors must provide a full hemispheric field of view with a high refresh rate in low cost and compact packages. This paper describes the design of a fast panomorph lens for the 8-12 μm IR band with hemispheric capabilities in a single integrated package that can be added to actual platforms to enhanced situation awareness systems. The various tradeoffs that were explored are detailed (material, size, relative cost, tolerances, F/#). The advantages and disadvantages of the panomorph design are compared to reflective, diffractive and other refractive solutions.

To meet today's demanding requirements for increased performance, reduced size, lower mass and lower cost, simple lenses containing multiple aspheric surfaces are required. It is now a common feature that the number of non-spherical surfaces used in an infrared lens design exceeds the actual number of lens elements. Judicious use of single-aspheric, dual-aspheric and asphero-diffractive surfaces provide additional degrees of freedom in the lens design. This is required not only to improve the imaging performance demanded by increasingly reduced pitch detectors, but to do so with solutions that are shorter and lighter whilst also offering excellent image uniformity with minimised stray light. Non-spherical surfaces also enable a greater diversity of materials to be used such that athermal solutions can be realised without the need for additional lens elements. This paper will review the range of applications that can be satisfied using no more than two optical components; examining the specific benefits that non-spherical surfaces can provide. Consideration will also be given to future developments where enhanced functionality can be achieved by using computational imaging techniques. Examples will be given for optical designs that are suitable for numerous military applications including weapon sights, driver's vision enhancement and remote weapon stations.

The increased desire for multispectral infrared optical systems in compact packages significantly complicates the optical design of such systems. Add in the fact that multiple spectral bands are now imaging on the same detector, and the optical designs become quite challenging. The availability of materials over the desired multiple spectral bands that transmit well with the desired dispersion properties further complicates the design. Designing optics for good performance in the SWIR (1.0 - 2.0μm) and the MWIR (3.5 - 5.0μm) bands is an example where this challenge can be significant. Many of the preferred optical materials in the MWIR start to cut off prior to reaching 1μm, or have dispersions that are very difficult to control over this broad of a spectral band. Reflective designs are often limited because of packaging limitations. In this paper, multiple approaches are designed and examined to find the best balance between risk, performance, and size. The analyzed design studies include the use of traditional MWIR materials, harmonic diffractive lenses, and alternative materials that will require further development to be used in a tactical environment.

This paper will explore an unwanted side effect of shortwave or near infrared optimized lens assemblies operating in low light conditions. Particular attention will be paid to those designs encountering a bright source in an otherwise low light scene; i.e. those with large dynamic ranges. The impact of bright features in very low levels can produce degrading artifacts or noise and greatly hinder image quality. The aforementioned effects will be demonstrated for both the SWIR optimized lenses and their visible light counterparts. The artifacts of traditional optical and mechanical geometries and their inherent problems will also be covered as well as how one might lessen their impact on image degradation and thereby improve system sensitivity.

Thin film metal oxide coatings have been used for commercial electromagnetic filters from the UV to infra red regions for over half a century. Deposition onto a substrate has typically been accomplished using vapor deposition techniques and more recently sol-gel methods. These coatings provide very good optical performance under abrasion, thermal cycles and variable humidity when applied on substrates with similar thermal and mechanical properties. When conventional metal oxide coatings are applied to flexible, relatively soft substrates such as polymers, mismatches in mechanical properties can reduce interfacial adhesion or accelerate mechanical failures. The authors recently showed that a thin film polymer nanocomposite can be applied on a polymer substrate and maintain adhesion even under high strains. This paper describes the demonstration of an IR mirror using fifteen discrete layers with an IR-reflectance that exceeds 90 percent at 1064 nm and transparent in the visible spectrum. We will present the results with thin film stacks containing over 15 discrete layers for IR mirror applications, and our recent work shows that the technology can produce thin film stacks containing 30 layers or more. Furthermore these coatings have high flexibility and can be applied to curved polymer substrates. These IR mirrors can withstand thermal cycling and large strains much better than those made using the state of the art techniques.

Coatings with high absorption or emission of thermal radiation are often required in infrared, space and cryogenic applications. It is much more difficult to generate a surface which is sufficiently "black" at cryogenic temperatures than at room or elevated temperatures. An experimental study was carried out to compare the thermal emissivity and absorptivity of a variety of black coatings on copper and aluminum substrates at temperatures in the range from 10 K to 300 K and the results are presented in this paper. The surfaces tested include paints and thin-film coatings.

Thanks to important development efforts completed internally and with the European Space Agency (ESA) funding, Air Liquide Advanced Technology Division (AL/DTA) is now in position to propose two Pulse Tube cooler systems in the 40-80K temperature range for coming Earth Observation missions such as Meteosat Third Generation (MTG), SIFTI, etc... The Miniature Pulse Tube Cooler (MPTC) is lifting up to 2.47W@80K with 50W maximal compressor input power and 10°C rejection temperature. The weight is 2.8 kg. The Large Pulse Tube Cooler (LPTC) is providing 2.3W@50K for 160W input power and 10°C rejection temperature. This product is weighing 5.1 kg. The two pulse tube coolers thermo-mechanical units are qualified against environmental constraints as per ESA ECSS-E-30. They are both using dual opposed pistons flexure bearing compressor with moving magnet linear motors in order to ensure very high lifetime. The associated Cooler Drive Electronics is also an important aspect specifically regarding the active control of the cooler thermo-mechanical unit during the launch phase and the active reduction of the vibrations induced by the compressor (partly supported by the French Agency CNES). This paper details the presentation of the two Pulse Tube Coolers together with the Cooler Drive Electronics aspects.

Thales Cryogenics has a long background in delivering cryogenic coolers with an MTTF far above 20.000 hrs for military, civil and space programs. Developments in these markets required continuous update of the flexure bearing cooler portfolio for new and emerging applications. The cooling requirements of new application have not only their influence on the size of the compressor, cold finger and cooling technology used but also on the integration and control of the cooler in the application. Thales Cryogenics developed a compact Cooler Drive Electronics based on DSP technology that could be used for driving linear flexure bearing coolers with extreme temperature stability and with additional diagnostics inside the CDE. This CDE has a wide application and can be modified to specific customer requirements. During the presentation the latest developments in flexure bearing cooler technology will be presented both for Stirling and Pulse Tube coolers. Also the relation between the most important recent detector requirements and possible available solutions on cryocooler level will be presented.

Infrared imagers play a vital role in the modern tactics of carrying out surveillance, reconnaissance, targeting and navigation operations. The cooled systems are known to be superior to their uncooled competitors in terms of working ranges, resolution and ability to distinguish/track fast moving objects in dynamic infrared scenes. These advantages are primarily due to maintaining the infrared focal plane arrays at cryogenic temperatures using mechanical closed cycle Stirling cryogenic coolers. Recent technological advances in industrial application of high-temperature (up to 200K) infrared detectors has spurred the development of linearly driven microminiature split Stirling cryogenic coolers having inherently longer life spans, lower vibration export and better aural stealth as compared to their rotary driven rivals. Moreover, recent progress in designing highly efficient "moving magnet" resonant linear actuators and dedicated smart electronics have enabled further improvements to the cooler size, weight, power consumption, cooldown time and ownership costs. The authors report on the development and project status of a novel microminiature split Stirling linear cryogenic cooler having a shortened to 19mm cold finger and a high driving frequency (90Hz). The cooler has been specifically designed for cooling 130K infrared sensors of future portable infrared imagers, where compactness, low steady-state power consumption and fast cool-down time are of primary concern.

Six Sigma method have been applied to manufacturing process of a rotary Stirling cooler: RM2. Name of the project is NoVa as main goal of the Six Sigma approach is to reduce variability (No Variability). Project has been based on the DMAIC guideline following five stages: Define, Measure, Analyse, Improve, Control. Objective has been set on the rate of coolers succeeding performance at first attempt with a goal value of 95%. A team has been gathered involving people and skills acting on the RM2 manufacturing line. Measurement System Analysis (MSA) has been applied to test bench and results after R&R gage show that measurement is one of the root cause for variability in RM2 process. Two more root causes have been identified by the team after process mapping analysis: regenerator filling factor and cleaning procedure. Causes for measurement variability have been identified and eradicated as shown by new results from R&R gage. Experimental results show that regenerator filling factor impacts process variability and affects yield. Improved process haven been set after new calibration process for test bench, new filling procedure for regenerator and an additional cleaning stage have been implemented. The objective for 95% coolers succeeding performance test at first attempt has been reached and kept for a significant period. RM2 manufacturing process is now managed according to Statistical Process Control based on control charts. Improvement in process capability have enabled introduction of sample testing procedure before delivery.

Novel compact and low power consuming cooled infrared thermal imagers as used in gyro-stabilized payloads of miniature unmanned aerial vehicles, Thermal small arms sights and tactical night vision goggles often rely on integral rotary micro-miniature closed cycle Stirling cryogenic engines. Development of EPI Antimonides technology and optimization of MCT technology allowed decreasing in order of magnitudes the level of dark current in infrared detectors thus enabling an increase in the optimal focal plane temperature in excess of 95K while keeping the same radiometric performances as achieved at 77K using regular technologies. Maintaining focal plane temperature in the range of 95K to 110K instead of 77K improves the efficiency of Stirling thermodynamic cycle thus enlarging cooling power and enabling the development of a mini micro cooler similar to RICOR's K562S model which is three times smaller, lighter and more compact than a standard tactical cryocooler like RICOR's K508 model. This cooler also features a new type of ball bearings and internal components which were optimized to fit tight bulk constraints and maintain the required life span, while keeping a low level of vibration and noise signature. Further, the functions of management the brushless DC motor and temperature stabilization are delivered by the newly developed high performance sensorless digital controller. By reducing Dewar Detector thermal losses and increasing the focal plane temperature, longer life time operation is expected as was proved with RICOR's K508 model. Resulting from this development, the RICOR K562S model cryogenic engine consumes 1.2 - 3.0 WDC while operating in the closed loop mode and maintaining the typical focal plane arrays at 200-100K. This makes it compatible with very compact battery packages allowing further reduction of the overall thermal imager weight thus making it comparable with the compatible uncooled infrared thermal imager relying on a microbolometer detector in terms of power consumption and bulk.

For different IR application specific cooler requirements are needed to achieve best performance on system level. Handheld applications require coolers with highest efficiency and lowest weight. For application with continuous operation, i.e. border surveillance or homeland security, a very high MTTF is mandatory. Space applications additionally require extremely high reliability. In other application like fighter aircraft sufficient cooling capacity even at extreme high reject temperatures has to be provided. Meeting all this requirements within one cooler design is technically not feasible. Therefore, different coolers designs like integral rotary, split rotary or split linear are being employed. The use of flexure bearings supporting the driving mechanism has generated a new sub-group for the linear coolers; also, the coolers may either use a motor with moving magnet or with moving coil. AIM has mainly focussed on long life linear cooler technology and therefore developed a series of moving magnet flexure bearing compressors which meets MTTF's exceeding 20,000h (up to 50,000h with a Pulse-Tube coldfinger). These compressors have a full flexure bearing support on both sides of the driving mechanism. Cooler designs are being compared in regard to characteristic figures as described above.

New methods of carrying out homeland security and antiterrorist operations call for the development of a new generation of mechanically cooled, portable, battery powered infrared imagers, relying on micro-miniature Stirling cryogenic coolers of rotary or linear types. Since split Stirling linearly driven micro-miniature cryogenic coolers have inherently longer life spans, low vibration export and better aural stealth as compared to their rotary driven rivals, they are more suitable for the above applications. The performance of such cryogenic coolers depends strongly on the efficacy of their electronic drivers. In a traditional approach, the PWM power electronics produce the fixed frequency tonal driving voltage/current, the magnitude of which is modulated via a PID control law so as to maintain the desired focal plane array temperature. The disadvantage of such drivers is that they draw high ripple current from the system's power bus. This results in the need for an oversized DC power supply (battery packs) and power electronic components, low efficiency due to excessive conductive losses and high residual electromagnetic interference which in turn degrades the performance of other systems connected to the same power bus. Without either an active line filter or large and heavy passive filtering, other electronics can not be powered from the same power bus, unless they incorporate heavy filtering at their inputs. The authors present the results of a feasibility study towards developing a novel "pumping" driver consuming essentially constant instant battery power/current without making use of an active or passive filter. In the tested setup, the driver relies on a bidirectional controllable bridge, invertible with the driving frequency, and a fast regulated DC/DC converter which maintains a constant level of current consumed from the DC power supply and thus operates in input current control mode. From the experimental results, the steady-state power consumed by the linear compressor remains the same as compared with the traditional sine wave driver, the voltage and current drawn from the battery pack is essentially free of low frequency ripple (this without use of any kind of filtering) and the overall coefficient of performance of the driver is in excess of 94% over the entire working range of supply voltages. Such a driver free of sine forming PWM stage and have reduced power peaks in all power conversion components.

One of the most important characteristics of a cryocooler is its useful operating life. Cryocoolers intended for space environments require cryocoolers with very long lifetimes, as the opportunity for servicing a failed unit is minimal. Tactical cryocooler requirements have increasing followed the trend of the space cryocooler, with required lifetimes reaching tens of thousands of hours. Three tactical one watt linear (OWL) cryocoolers at Carleton Life Support Systems, Inc. (CLSS) of Davenport, IA, recently surpassed 20,000 hours of operation. Acceptance tests show that the performance of the cryocoolers has not significantly degraded over this timeframe. This paper reports the performance of the cryocoolers over the span of the test. Steady-state and cooldown performance at various ambient temperatures are reported.

This paper presents digital image fusion (enhanced A+B) systems in color imaging and low light target applications. This paper will discuss first the digital sensors that are utilized in the noted image fusion applications which is a 1900x1086 (high definition format) CMOS imager coupled to a Generation III image intensifier for the visible/near infrared (NIR) digital sensor and 320x240 or 640x480 uncooled microbolometer thermal imager for the long wavelength infrared (LWIR) digital sensor. Performance metrics for these digital imaging sensors will be presented. The digital image fusion (enhanced A+B) process will be presented in context of early fused night vision systems such as the digital image fused system (DIFS) and the digital enhanced night vision goggle and later, the long range digitally fused night vision sighting system. Next, this paper will discuss the effects of user display color in a dual color digital image fusion system. Dual color image fusion schemes such as Green/Red, Cyan/Yellow, and White/Blue for image intensifier and thermal infrared sensor color representation, respectively, are discussed. Finally, this paper will present digitally fused imagery and image analysis of long distance targets in low light from these digital fused systems. The result of this image analysis with enhanced A+B digital image fusion systems is that maximum contrast and spatial resolution is achieved in a digital fusion mode as compared to individual sensor modalities in low light, long distance imaging applications. Paper has been cleared by DoD/OSR for Public Release under Ref: 08-S-2183 on August 8, 2008.

In this paper we present a VNIR solid state sensor technology suitable for next generation fused night vision systems. This technology is based on a highly optimized low power 0.18um CMOS image sensor (CIS) process. We describe a 320(H) x 240(V) pixel prototype sensor based on this technology. The sensor features 5T pixels with pinned photodiodes on a 6.5μm pitch with integrated micro-lens. The 5T pixel architecture enables both correlated double sampling (CDS) and a lateral anti-blooming drain. The measured peak quantum efficiency of the sensor is greater than 50% at 600nm, and the read noise is less than 1e- RMS at room temperature. The sensor does not have any multiplicative noise. The full well capacity is greater than 40ke-, the dark current is less than 3.8pA/cm2 at 20ºC, and the MTF at 77 lp/mm is 0.4 at 600nm. The sensor also achieves an intra-scene linear dynamic range of greater than 90dB (30000:1) at room temperature.

The FELIN French modernization program for dismounted combat provides the Armies with info-centric systems which dramatically enhance the performances of the soldier and the platoon. Sagem now has available a portfolio of various equipments, providing C4I, data and voice digital communication, and enhanced vision for day and night operations, through compact high performance electro-optics. The FELIN system provides the infantryman with a high-tech integrated and modular system which increases significantly their detection, recognition, identification capabilities, their situation awareness and information sharing, and this in any dismounted close combat situation. Among the key technologies used in this system, infrared and intensified vision provide a significant improvement in capability, observation performance and protection of the ground soldiers. This paper presents in detail the developed equipments, with an emphasis on lessons learned from the technical and operational feedback from dismounted close combat field tests.

Germany's future ground soldier program is entitled "IDZ-ES-: Infanterist der Zukunft - Erweitertes System". This latest "ES - enhanced system" is embedded in the specifications of a network-centric warfare concept with highly equipped soldiers of outstanding capabilities, based on new components. One of them will be the handheld multifunctional thermal imager which provides full C4ISTAR capability. This light weighted instrument includes a thermal imager to detect an object at 5000m, recognize it at 4200m and identify it at 2100m. The IR Image channel can be superimposed with a visual daylight image that is recorded by an integrated CCD-camera. The image which is available on two Organic Light Emitting Displays can be viewed through a binocular viewer. It also provides information of the command and control system. With the laser range finder, the Digital Magnetic Compass and GPS it is possible to measure one's own and the target's position. This information and live video sequences can be transferred to the C4I-alliance in wireless mode. It is possible to annotate seen objects with symbols and information. By networking, team members and control officers will have superior information along with possibilities for control of impact and can execute their mission more efficiently.

The Small Arms Video Sight is part of the optronical sights developed for the German IdZ-ES program (German Army Soldier-of-the Future Program - Enhanced System) [1]. The aim of the development was to use this highly integrated sight on three different rifles (G36 = the assault rifle of the German soldier optional with a 40mm underslung grenade launcher, MG 4 = a light machine gun , PZF3 = a 60mm / 110mm bazooka). The Video Sight will be used for observation, target detection, recognition and identification, direct and indirect aiming and shooting with ballistic calculation and aiming mark correction, still and video picture capturing and wireless transmission, determination of a located target position by distance and angle to the own position and so on. To perform all these tasks the Video Sight is equipped with an uncooled IR and a CCD camera, a laser range finder, a digital compass, angle sensors, electronic display, all this sensors highly integrated and controlled by an operating system.

The Integrated Soldier System Project (ISSP) is the cornerstone of Canada's future soldier modernization effort, which seeks to "significantly enhance tactical level individual and team Lethality, Mobility and C4I performance in the complex, network-enabled, command-centric, effects-based digitized battlespace." This capital acquisition project is supported by a number of R&D Technology Demonstration Projects within Defence R&D Canada. Several of these projects focus on the human factors aspects of future technologies, such as IR sensors. The Soldier Information Requirements Technology Demonstration (SIREQ TD) project examined the performance impact of NVGs, LWIR imaging systems, and fused systems (both optical and digital fusion) on target detection, recognition and identification. NVGs were shown to provide good identification performance while LWIR systems excelled in detection tasks. Fused systems show promise of augmenting the respective stand alone capabilities of each sensor type, but more work is required to optimize fusion algorithms. The Soldier Integrated Headwear Technology Demonstration (SIHS TD) project is looking at the human factors aspects of mounting a range of vision enhancement sensors on a helmet, including optimal placement of both sensors and displays with respect to center of mass, total head borne weight, and visual offset and parallax issues. Overall headwear system weight should be less than 2.5 kg, and if an offset from the eye is required then a horizontal offset (vice vertical or oblique) of the sensor appears most acceptable. These findings have implications on the design of future IR and fused sensor systems for dismounted soldiers.

In recent years the TED system has been under development, starting from new SWIR sensor technology, optics and real-time sensor technologies and following with complete system architecture as a soldier mounted optical gun shot detection system with high precision and imaging means. For the first time, the modules and the concept of operation of the system will be explained, with emphasis on new sensor-to-shooter capabilities. Actual field trial results will be shown.

The latest generation of heavily armored vehicles and the proliferation of IEDs in urban combat environments dictate that electro-optical systems play a greater role in situational awareness for ground vehicles. FLIR systems has been addressing the needs of the ground vehicle community by developing unique sensor systems combining thermal imaging and electro-optical sensors, advanced image processing, and networking capabilities into compact, cost effective packages. This paper will discuss one of those new products, the WideEye II. The WideEye II combines long wave infrared and electro-optical sensors in a 180 degree field of view, single integrated package to meet the critical needs of the warfighter. It includes seamless electronic stitching of the 180 degree image, and state of the art networking capability to allow it to be operated standalone or to be fully integrated with modern combat vehicle systems. The paper will discuss system tradeoffs and capabilities of this new product and show potential applications for its use.

BAE Systems and the US Army have conducted a series of investigative studies and on-vehicle evaluations of 360°, indirect viewing and ground vehicle vision systems. The studies consider a range of system options for establishing a close-in, real-time, image-based situational awareness system for day and nighttime vehicle operation. Multi-spectral imaging assets were utilized in combination with image processing techniques to extend situational awareness and support the operation of armored vehicles during "closed-hatch" exercises. The study findings include the central role of uncooled IR Microbolometers as a foundational element of day/night vehicle indirect vision systems.

SAPIR system provides a suite of IR based situation awareness functions offered as add on system for ELISRA PAWS family of missile warning solutions. A major operational need for airborne platforms flying in formation is automatic collision alert capability. By using covert IR-MWS technology SAPIR passively tracks and monitors wingman position thereby enabling aircrew to focus on mission goals without compromising their safety. The paper presents results of operational problem study, system design and field testing demonstration of performance for SAPIR collision alert function targeting helicopter fleets.

Self protection of airborne assets has been important to the Air Force and DoD community for many years. The greatest threats to aircraft continue to be man portable air defense missiles and ground fire. AFRL has been pursuing a near-IR sensor approach that has shown to have better performance than midwave IR systems with much lower costs. SIMAC couples multiple spatial and temporal filtering techniques to provide the needed clutter suppression in the NIR missile warning systems. Results from flight tests will be discussed .

Over the past few years, the Missile Defense Agency Advanced Technology Directorate (MDA/DV) has funded the development of a new III-V infrared (IR) sensor focal plane material: type II strained layer superlattice (SLS). Infrared sensors are crucial to missile defense capabilities for target acquisition, tracking, discrimination, and aim point selection; they serve other military sensing applications as well. Most current infrared military systems use mercury-cadmiumtelluride (HgCdTe), a II-VI semiconductor material, for long-wavelength (LW) (8-12 um) focal plane array (FPA) applications. It is difficult to achieve large-format FPAs in HgCdTe at long wavelengths (LW) due to their low yield. The situation is aggravated by the limitation of the small cadmium-zinc-telluride (CdZnTe) substrates. SLS is the only known IR material that has a theoretical prediction of higher performance than HgCdTe. Over the past three years, SLS technology has progressed significantly, demonstrating experimentally its potential as a strong candidate for future highperformance IR sensor materials. In this paper, we will discuss the most recent progress made in SLS. We will also discuss MDA's new direction for this technology development. The plan is to use a horizontal integration approach instead of adhering to the existing vertical integration model. This new horizontal approach is to increase the number of industrial participants working in SLS and leverage existing III-V semiconductor foundries. Hopefully it will reduce the cost of SLS IR technology development, shared foundry maintenance, and future SLS production.

The development of type-II InAs/GaSb superlattice (SL) detectors with nBn and pin designs for the long wave infrared (LWIR) spectral region are discussed. First, SL growth optimization for LWIR region is explained, then the structures based on LWIR nBn and pin are presented. Comparison of optical characterization for the identical SL structures based on the nBn and pin designs is reported. Dark current density of 0.001 A/cm² at 100 mV for nBn as compared to 0.2 A/cm² for pin devices shows a reduction of dark current density using the nBn design. At 77 K, the peak responsivity and detectivity are measured to be 5.86 A/W and 3.08 × 10¹⁰ Jones for the nBn and 1.49 A/W and 4.2 × 10⁹ Jones for the pin based design, respectively.

Recent advances in growth techniques, structure design and processing have lifted the performance of Type-II InAs/GaSb superlattice photodetectors. The introduction of a M-structure design improved both the dark current and R0A of Type-II photodiodes. This new structure combined with a thick absorbing region demonstrated background limited performance at 77K for a 300K background and a 2-π field of view. A focal plane array with a 9.6 μm 50% cutoff wavelength was fabricated with this design and characterized at 80K. The dark current of individual pixels was measured around 1.3 nA, 7 times lower than previous superlattice FPAs. This led to a higher dynamic range and longer integration times. The quantum efficiency of detectors without anti-reflective coating was 72%. The noise equivalent temperature difference reached 23 mK. The deposition of an anti-reflective coating improved the NEDT to 20 mK and the quantum efficiency to 89%.

InAs/GaSb type-II short-period superlattice (SL) photodiodes have been shown to be very promising for 2nd and 3rd generation thermal imaging systems with excellent detector performance. A multi-wafer molecular beam epitaxy (MBE) growth process on 3"-GaSb substrates, which allows simultaneous growth on five substrates with excellent homogeneity has been developed. A reliable III/V-process technology for badge processing of single-color and dual-color FPAs has been set up to facilitate fabrication of mono- and bi-spectral InAs/GaSb SL detector arrays for the mid-IR spectral range. Mono- and bispectral SL camera systems with different pitch and number of pixels have been fabricated. Those imaging systems show excellent electro-optical performance data with a noise equivalent temperature difference (NETD) around 10 mK.

We have evaluated selective doping techniques for the fabrication of type II LWIR superlattice planar detectors. Ion-implantation and diffusion of dopants were evaluated for selective doping of the electrical junction region in planar photodiodes. Residual damage remains when superlattice structures are implanted with Te ions with an energy of 190 keV and a dose of 5x10¹³ cm^-2, at room temperature. Controlled Zn diffusion profiles with concentrations from 5x10¹⁶ to > 5x10¹⁸ cm^-3 in the wide bandgap cap layer was achieved through a vapor phase diffusion technique. Planar p-on-n diodes were fabricated using selective Zn diffusion. The I-V characteristics were leaky due to G-R and tunneling in the homojunction devices, for which no attempts were made to optimize the n-type absorber doping level. Work is underway for the implementation of planar diodes with the n-on-p architecture through selective Te diffusion. Due to increased minority carrier lifetimes for p-type InAs/GaSb superlattice absorber layers, planar device with the n-on-p architecture have the potential to provide improved performance as compared to the p-on-n counterparts.

In recent years, Type II InAs/GaSb superlattices grown on GaSb substrate have achieved significant advances in both structural design and material growth, making Type II superlattice infrared detector a rival competitor to the state-of-the-art MCT technology. However, the limited size and strong infrared absorption of GaSb substrates prevent large format type-II superlattice infrared imagers from being realized. In this work, we demonstrate type-II superlattices grown on GaAs substrates, which is a significant step toward third generation infrared imaging at low cost. The device performances of Type II superalttice photodetectors grown on these two substrates are compared.

In this work the current versus voltage data of a p-n+ junction is converted into minority carrier lifetime data. Space charge recombination currents dominate at modest reverse bias at 80K and taking the dominant recombination centers to be located at the intrinsic Fermi level, the lowest minority carrier lifetime τ₀ is determined to be 35ns. This single Shockley-Read-Hall carrier recombination parameter provides an excellent fit to the data over temperature range 40K≤ T≤ 130K; the 35ns minority carrier lifetime also explains the quantum efficiency data. The transition from diffusion to space charge currents occurs for temperatures, T ≤ 100K. For T≤ 40K trap assisted tunneling is the dominant current component. Based on imaging system requirements to be near background limited for photon flux ≈ 10¹⁵ ph/cm²-s and detector temperature of 80K, the minority carrier lifetime will need to be increased by one order of magnitude.

Sofradir IR detectors are being deployed in a lengthening line of space applications (earth observation, atmospheric observation, scientific missions, etc...). At first glance, one may ask what do detectors for space applications have in common with detectors for tactical applications? On the one hand, space applications require far fewer quantities and IR detector reliability and electro-optical performances must be exceptionally high. Tactical applications, on the other hand, look to quantities in the thousands per year, delivered at low cost. As opposed to focusing on the differences, Sofradir is taking advantage of these two areas. Firstly, space applications are developing new advances and technologies that can later be introduced in the production of IR detectors for tactical applications, thereby increasing their quality and reliability. In addition, Sofradir can better satisfy space application requirements for failure rates, as these can only be demonstrated with the large number of detectors manufactured, which tactical applications provide. This advantage is only possible because the core of the technologies and manufacturing processes are common to both applications. As a result, this approach offers a continuous cycle for reliability of IR detectors, accelerating reliability growth in production, and at the same time meeting requirements for space applications.

The predominant spectral bands for IR applications are the 3-5μm MWIR and 8-10μm LWIR. AIM covers all these bands since many years with a mature MCT technology. For weight, size, power consumption and - last but not least - cost reduction, detection modules for these applications move to a pitch of 15μm. This is in both bands still a good match referring to the optical blur spot size and detector performance. Due to the compact design, the modules are equally well suited for new programs as well as retrofits of 1st GEN systems. Typical configurations at AIM are a 640x512 MWIR module, achieving an NETD < 25 mK @ F/4.6 and 5 ms integration time equivalent to half well fill conditions and an LWIR version with NETD < 30 mK @ F/2 and 110μs integration time. The modules are available either with an integral rotary cooler for portable applications which require minimum cooling power or a split linear cooler with a flexure bearing compressor providing long lifetimes with a MTTF >20,000h as required e.g. for warning sensors in 24/7 operation. A new field of applications supplied by AIM is the short wave infrared SWIR. The major advantage of MCT, the tunable bandgap i.e. cut-off wavelength, allows to match various requirements. So far specifically driven by spaceborne programs, a 1024x256 SWIR focal plane array (FPA) integrated detector cooler assembly (IDCA) with flexure bearing cooler and pulse tube cold finger was developed. The same technology including charge transimpedance amplifier for the low flux in the SWIR is available in a half TV 384x288 configuration. The read-out integrated circuit (ROIC) provides among other features 8 outputs for high frame rates up to 450Hz. Again for spaceborne commercial but also military applications like sensors in ballistic missile defense systems AIM develops MCT based very long wave (VLWIR) detectors with a cut-off wavelength >15μm. The current status and trends at AIM on IR detection modules sensitive in spectral ranges from short wave IR (SWIR) to very long wave IR (VLWIR) together with the requirements of the demanding applications are summarized.

Detectors that have broadband response from the visible (~ 400 nm) to near infrared (~ 2.5 μm) have remote sensing hyperspectral applications on a single chip. 2.2 and 2.5 μm cutoff detectors permit operation in the 200 K range. The DRS HDVIP detector technology is a front side illuminated detector technology. Consequently, there is no substrate to absorb the visible photons as in backside-illuminated detectors and these 2.2 and 2.5-μm-cutoff detectors should be well suited to respond to visible light. However, HDVIP detectors are passivated using CdTe that absorbs the visible light photons. CdTe with a direct bandgap ~ 1.6 eV strongly absorbs photons of wavelength shorter than about 800 nm. Detectors in 320 x 6 arrays with varying thickness of CdTe passivation layers were fabricated to investigate the visible response of the 2.5-μm-cutoff detectors. The SWIR HDVIP detectors have well known high quantum efficiency (QE) in the near infrared region. Focus here was in acquiring array level data in the visible region of the spectrum. 320 x 6 FPA QE and NEI data was acquired using a 642 nm narrow band filter with 50 % points at 612 nm and 698 nm. The array QE average is ~ 70 % for the array with CdTe passivation thickness = 44.5 nm. The NEI is ~ 5 x 10¹⁰ ph/cm2/s at a flux Φ = 5.36 x 10¹³ ph/cm²/s. QE for an array with CdTe passivation thickness = 44.5 nm is ~ 10 % higher than an array with CdTe passivation thickness = 79.3 nm. In addition, a model that takes into account the complex optical properties of every layer in the HDVIP photodiode architecture was developed to predict the QE of the detectors in the near infrared and visible wavelength regions as a function of CdTe thickness. Measured QE as a function of wavelength is not a good match to the model QE probably due to limitations in the measured QE and knowledge of optical constants that are input into the model.

Raytheon Visions Systems (RVS) is furthering its capability to deliver state-of-the-art high performance large format HgCdTe focal plane arrays (FPAs) for dual-band long-wavelength infrared (LWIR) detection. Missile seekers are designed to acquire targets of interest at long ranges and discriminate targets from clutter. The use of dual-band long wavelength infrared detector technology provides the ability for these seekers to combine these operations into the same package with enhanced performance. Increasing the format size of dual-band longwavelength FPAs and tailoring the detector design for specific long-wavelength bands enables seekers to be designed for increased field-of-view, longer target acquisition ranges, and improved accuracy. This paper will review in further detail the aspects of detector design, MBE wafer growth, wafer fabrication, and detector characterization that are contributing to development and demonstration of high performance large format dual-band LWIR FPAs at RVS.

This paper describes the fabrication and performance of our LW Hawk arrays. These are Full-TV (640x512) LW infrared detectors at small pitch (16 μm) made from HgCdTe grown by Metal Organic Vapour Phase Epitaxy (MOVPE). The detectors are staring, focal planes consisting of HgCdTe mesa-diode arrays bump bonded to silicon read-out circuits. The HgCdTe structure is grown on GaAs and consists of an absorber layer sandwiched between wider band-gap cladding layers. Device processing is wafer-scale. This is an extension of the work reported in previous years with the innovation of dry etching for mesa isolation. The GaAs substrate is removed after bump bonding to minimise the thermal stress on cooling. The technology will be described. Results will be presented which show operability of 99.96% with a median NETD of 32 mK, reducing to 22 mK in binning mode. The results of various imaging trials will also be presented.

The very long infrared wavelength (>14μm) is a very challenging range for the design of large HgCdTe focal plane arrays. As the wavelength gets longer (ie the semiconductor gap gets smaller), the physic of photodiodes asks for numerous technological improvements to keep a high level of detection performance. DEFIR (LETI-Sofradir common research team) has been highly active in this field during the last few years. The need (mainly expressed by the space industry ESA and CNES) of very long wave focal plane arrays appears very demanding in terms of dark current, defect density and of course quantum efficiency. This paper aims at presenting a status of long and very long wave focal plane array development at DEFIR for three different ion implanted technologies: n on p mercury vacancies doped technology, n on p extrinsic doped technology, and p on n arsenic on indium technology. Special focus is done to 15μm cut off n/p focal plane array fabricated in our laboratory demonstrating high uniformity, diffusion and shot noise limited photodiodes at 50K.

Selex Sensors and Airbourne Systems has been active in developing Very Long Wave arrays for space applications under a contract of the European Space Agency. Arrays have been demonstrated with a 15 μm cut-off operating at 55 K. The technology is an extension of our standard LW, described elsewhere, using MOVPE layers grown on GaAs to provide a low cost, large area capability with state-of-the-art performance. The test vehicle for the VLW development is a direct injection 320 x 256, 30 μm pitch ROIC with a well capacity of 20 million electrons. While it may be considered that direct injection is not ideal for typical diode impedances expected in the VLW, and alternatives are in design, it is a testament to our technology that the diodes have sufficient dynamic resistance to allow this approach. Our diode design provides low diffusion currents such that at these operating temperatures the arrays are largely limited by trap assisted tunnelling (TAT). Results of dark current as a function of voltage and temperature will be presented along with the array electro-optical performance.

This paper presents recent development made at CEA-LETI on manufacturing and characterization of planar p-on-n HgCdTe photodiodes on long-, mid- and short-wavelength. HgCdTe (MCT) layer was grown both by liquid-phase epitaxy (LPE) and by molecular beam epitaxy (MBE) on lattice matched CdZnTe (CZT). The n-type MCT base layer was obtained by indium doping. Planar p-on-n photodiodes were manufactured by arsenic doping, which has been activated by post-implanted annealing in Hg overpressure. As incorporation is achieved either by implantation or by incorporation (during MBE growth). Electro-optical characterizations on these p-on-n photodiodes were made on FPAs. Results show excellent operabilities (99.95% with ±0.5×mean value criterion) in responsivity and NETD and background limited photodetectors. For long-wavelength FPAs, dark current is very low, leading to a R0A product comparable to the state of the art at cut-off wavelength of λc = 9.2 μm. MBE mid-wavelength FPAs present very low responsivity dispersion, reaching 1.1%. Comparisons are made between implantation and growth incorporation As doping technologies.

We have developed various types of photodetectors operating without cryocooling. Initially, the devices were mostly used for uncooled detection of CO₂ laser radiation. Over the years the performance and speed of response has been steadily improved. At present the uncooled or Peltier cooled photodetectors can be used for sensitive and fast response detection in the MWIR and LWIR spectral range. The devices have found important applications in IR spectrometry, quantum cascade laser based gas analyzers, laser radiation alerters and many other IR systems. Recent efforts were concentrated on the extension of useful spectral range to >13 μm, as required for its application in FTIR spectrometers. This was achieved with improved design of the active elements, use of monolithic optical immersion technology, enhanced absorption of radiation, dedicated electronics, series connection of small cells in series, and last but not least, applying more efficient Peltier coolers. Practical devices are based on the complex HgCdTe heterostructures grown on GaAs substrates with MOCVD technique with immersion lens formed by micromachining in the GaAs substrates. The results are very encouraging. The devices cooled with miniature 4 stage Peltier coolers mounted in TO-8 style housings show significant response at wavelength exceeding 16 μm.

Experimental results concerned morphology improvement of HgCdTe layers grown by MOCVD on GaAs substrates are presented. Selected growth parameters on morphology state have been discussed. The substrate issues like its quality and crystallographic orientation as well as misorientation play considerable role in final layer smoothness. We study HgCdTe layer thickness on its surface roughness. The MBE/MOCVD combination method had been adopted for CdTe buffer layer deposition. Extensive characterization studies using accessible equipment and methods: atomic force microscopy (AFM), secondary electron microscopy (SEM), laser scatterometer and Nomarski microscopy have provided invaluable information about the connection between defect formation and the influence of specific growth parameters.

We have previously reported on the initial development of a multi-linear uncooled microbolometer FPA for space applications. The IRL512 FPA features three parallel lines of 512 pixels on a 39 micron pixel pitch with parallel integration of all pixels, a complete detector bridge per pixel for offset and substrate temperature drift compensation, and one 14-bit digital output bus per line. The FPA achieves an NETD below 45 mK over the LWIR spectral band with 50 ms integration time, 300 K scene temperature, and f/0.87 optics. In the context of the NIRST instrument for the upcoming SAC-D/Aquarius earth observation mission, MWIR and LWIR optimized versions of the IRL512 in radiometric packages including integrated stripe filter and radiation shield have recently successfully undergone screening and qualification campaigns. The qualification strategy consists of part element and device qualification including proton and total dose radiation, shock, vibration, burn-in, and thermal cycling. The test conditions and results will be reviewed. The thermal resolution of the current generation of radiometrically packaged IRL512 FPA in the NIRST instrument is below 500 mK with an 0.9 micron spectral bandwidth centred at 10.85 μm, 50 ms integration time, the NIRST f/1 optics, and 300 K scene temperature.

In the observation and surveillance fields, there is an increasing demand for infrared modules that can be rapidly turned into a complete autonomous device whether it is for military, security or industrial purposes. Based on this concept, INO has developed a modular 16 bit infrared camera core. The tool can be used to provide a rapid evaluation of an application concept. Moreover, a complete device can be rapidly designed and build once the concept has been demonstrated. The IRXCore-640 camera core, integrating a 640 x 480 pixel uncooled FPA and providing a 16-bit raw signal output at 60 Hz, gives total access to the detector configuration parameters to ease developers integration process. TECless operation minimizes module size and power consumption. The camera core can be configured at the factory for outdoors operation from -30°C to +60°C with 200°C scene dynamic range at maximum sensitivity. The device can be used with refractive optics or catadioptric optical objectives. Windowing capability provides flexibility in frame frequency, sensitivity selection, and a choice of operating field of view. High resolution/high sensitivity can be achieved. In this paper, the camera core will be reviewed as well as its performances. The control software functionalities are detailed and some typical imaging examples will be presented.

Pyroelectric devices require a change in temperature in order to generate a useful signal. For this reason, Thin Film Ferroelectric (TFFE) sensors require a chopping system to modulate the incident thermal radiation. This chopping or modulation process translates the signal of interest from DC to the chopping frequency, enabling the use of filtering techniques to minimize the effects of 1/f noise.

Polycrystalline PbSe technology is today an emerging technology thanks to the method for processing monolithic detectors based on a Vapor Phase Deposition (VPD) technique developed at CIDA. The first monolithic device was successfully processed in 2007 (16x16 FPA, 200 μm pitch and Digital Pixel Sensor (DPS) concept). Remarkable progress has been made improving some technological steps and developing tools for processing high signal rates. In this work, low resolution IR images taken up to 20 Kfps with a real uncooled device are shown. These results represent an important milestone and allocate the VPD PbSe technology among the major players within the domain of uncooled IR detectors. It is a photonic detector suitable for being used in low cost IR imagers sensitive in the MWIR band and with frame rates above 10,000 Hz. The number of applications is therefore huge, some of them specific, such as sensor for Active Protection Systems or low cost seekers.

We developed vacuum packaging equipment and low-cost vacuum packaging technology for the mass production of uncooled IRFPAs. The equipment consists of two chambers with identical construction. Two-chamber architecture provides flexibility in the vacuum packaging process, so we can bake the components and achieve getter activation by heating, stem/cap soldering, and cap/window soldering in a series under high-vacuum conditions. Heaters and component-holding jigs are made of graphite to assure rapid and uniform heating to 500°C. The batch size is 27 if we choose a 15-mm diameter TO8 package and can be increased by enlarging the graphite heater area. We also developed a micro-vacuum gauge to evaluate the vacuum level in encapsulated packages. The operation principle of this vacuum gauge is based on thermal conduction by air molecules. It can be integrated in IRFPA chips since the fabrication process is compatible with that for IRFPAs. We encapsulated the vacuum gauges in TO8 packages with our vacuum packaging equipment, and confirmed that the pressure in fabricated packages is sufficiently low for high performance IRFPA operation (<< 1 Pa) with the micro-vacuum gauges.

The high level of accumulated expertise by ULIS on uncooled microbolometers TEC-less operation enables ULIS to develop 384 x 288 (1/4 VGA) IRFPA format with 25μm pixel-pitch especially designed for TEC-less application. This detector, while keeping all the performances and all the innovations developed on previous ULIS ROIC (NETD performance, detector configuration by serial link, low power consumption and wide electrical dynamic range ...), can be operated on a wide range of ambient temperature, with constant settings. We present in this paper the electro-optical performances and the TEC-less capability of this device. The thermal behavior is described in detail.

Uncooled TIS is in the spotlight for its small size and low-voltage operation for personal and portable use compare to other TIS. Generally, uncooled TIS using temperature control by TEC converts the gap between TEC temperature and input-image into voltage by ROIC and outputs the analog image. For cooled detector, it is possible to block undesirable infrared input since F number of the optics and the detector are same but for uncooled detector, it is easy to get undesirable infrared input around because the F numbers are different. It becomes more obvious when temperature gap between the equipment and background gets bigger. For TIS, background temperature easily changes inside the system and around the detector because the radiating heat from the electrical circuit inside the system is getting higher as usage time passes, and it makes worse the non-uniformity output characteristics of the detector. In particular, the temperature change of the system itself which depends on its setting position and other temperaturechanging factors like electrical circuit inside the system make the additional non-uniformity worse which caused by infrared photon radiates from structures which includes optics and detector. This article would indicate the method of minimizing its image blurring which originates from the F number gap between optics and detector.

The paper describes the layout and essential properties of single-element detectors with an innovative layout of the pyroelectric chip. The pyroelectric material used is lithium tantalate. Geometry, arrangement and bonding of the responsive element ensure a very high specific detectivity D* combined with very low microphonics. The properties of both the newly developed sensors and commercially available pyroelectric detectors are compared. Using the results of simulations of the thermal and optical conditions in the environment of the responsive element, the chip layout was optimised to obtain a high signal-to-noise ratio. Furthermore, simulation calculations were performed using the FEM program ANSYS to minimise the signal voltage of the detector in case of mechanical excitation. For this purpose, a three-dimensional model of the assembled and bonded LiTaO3 chip was created. On the basis of the simulated layout, a suitable manufacturing technology was developed and complete detectors were built. It was shown that thanks to these detectors the specific detectivity D* assumed values of (500 K; 10 Hz; 1 Hz; τW = 1, α ≈ 0.9) ≥ 1.8 x 10⁹ cmHz^1/2W^-1 for a responsive area of [1x1] mm². The measurement of the acceleration sensitivity produced typical values of RVB < 10 μV/9.81 ms^-2 (fB < 1000 Hz).

This paper presents a real time implementation of Non Uniformity Correction (NUC). Two point correction and one point correction with shutter were carried out in an uncooled imaging system which will be applied to a missile application. To design a small, light weight and high speed imaging system for a missile system, SoPC (System On a Programmable Chip) which comprises of FPGA and soft core (Micro-blaze) was used. Real time NUC and generation of control signals are implemented using FPGA. Also, three different NUC tables were made to make the operating time shorter and to reduce the power consumption in a large range of environment temperature. The imaging system consists of optics and four electronics boards which are detector interface board, Analog to Digital converter board, Detector signal generation board and Power supply board. To evaluate the imaging system, NETD was measured. The NETD was less than 160mK in three different environment temperatures.

This paper describes a differential readout circuit technique for uncooled Infrared Focal Plane Arrays (IRFPA) sensors. The differential operation allows an efficient rejection of the common-mode noise during the biasing and readout of the detectors. This has been enabled by utilizing a number of blind and thermally-isolated IR bolometers as reference detectors. In addition, a pixel-wise detector calibration capability has been provided in order to allow efficient error corrections using digital signal processing techniques. The readout circuit for a 64×64 test bolometer-array has been designed in a standard 0.35-μm CMOS process. Circuit simulations show that the analog readout at 60 frames/s consumes 30 mW from a 3.3-V supply and results in a noise equivalent temperature difference (NETD) of 125 mK for infrared optics.

This paper proposes a new method to suppress the bias heating effect of the resistive uncooled microbolometer detectors. The bias heating effect especially limits the performance where long integration time and large detector bias voltages are required. The proposed method uses a number of reference detectors for each column of the FPA where the reference detectors have an optimized thermal conductance and are covered by an infrared reflecting material in order to achieve high infrared blindness. The heating and cooling durations of the reference detectors are optimized so that the heating characteristic and the stabilized temperature of the reference detectors are similar to those of the active detectors. Additionally, a resistance mismatch between the reference detectors and the active detectors is introduced in order to match the thermal characteristics and to obtain maximum bias heating cancellation. This intentional mismatch is compensated with a series-connected CMOS resistor to keep the balance in the CTIA circuit. The simulation results show that it is possible to cancel 97.6% of the resistance change due to bias heating with the use of this method, making it possible to increase the gain of the column readout by a factor of about 41.

This paper presents a column-based, two-stage, 12-bit analog-to-digital converter structure designed for uncooled microbolometer arrays. On-chip analog-to-digital converters prevent the degradation of sensitive analog output by external noise sources as well as providing a more integrated functionality. Despite these advantages, the area and power constraints limit the usage of high performance converters. This paper presents a new structure that provides a balance between area, power, and performance. The structure is composed of two stages: a tracking ADC stage running at each column during integration and a successive approximation ADC stage which is shared by a number of columns depending on the array size and operation frequency. The tracking ADC operates during the integration time, while the second ADC starts after the integration is completed. The converter includes self-calibration to lower the effect of process variations and digital correction mechanisms to eliminate the need for low-offset comparators. The simulations and theoretical calculations based on the simulation results show that the total power dissipation of the proposed structure will be approximately 73.7 mW and 88.4 mW on a 320x240 array operating at 60 Hz and 384x288 array operating at 50 Hz, respectively.

Arrays of independently tunable MEMS Fabry-Perot filters have been developed that enable spectral tuning over the range of 11 - 8 microns with a filter bandwidth of ~ 120 nm. Actuation is provided using a MEMS driver IC that is hybridized to the MEMS chip. Combining the filter array with an IR FPA enables spatially-resolved spectral tuning in a compact architecture. Tunable spectral response data from the first integrated tunable filter / FPA device are presented.

Dual band infrared imagers require a similar set of filters as are needed by single band infrared imagers but with the added requirement of high transmission in the mid and far infrared. The design of discrete layer filters with optimized dual band transmission is investigated for three types of filters. These are a visible-infrared beamsplitter, a long wavelength edge filter and a dual bandpass cold filter. These designs illustrate the role that harmonic reflection bands can play in the design of dual band filters. The visible reflection beamsplitter design does not have harmonics in the infrared but requires additional layers to reduce reflection at mid and long wavelengths. The long wavelength edge filter requires suppression of the second and third harmonics while the sensor band pass cold filter can use harmonics to advantage. Design techniques are discussed and the results of an initial set of fabrication runs are presented to assess the sensitivity of example designs to manufacturing errors.

Bandpass filters transmitting the 3.5 to 5.0μm atmospheric window while simultaneously blocking the 4.3μm CO2 absorption band are in demand. However, realization of these dual bandpass filters is challenging from the standpoint of coating design, material selection, and manufacturing process. JDSU's Ucp-1 magnetron sputtering platform is ideally suited to the production of these types of filters. It enables the use of coating materials with higher transmission and lower temperature shifts than conventional (i.e. thermally evaporated) MWIR materials. Ucp-1 also has excellent layer thickness control, which allows complex designs to be realized. The performance of a dual bandpass filter manufactured for AFRL as part of their "Exploration of Novel Band-pass Filter Designs" program is discussed. The filter achieved average transmission in the passbands of greater than 94% with filter slopes of 1.1% or less. Blocking of the CO2 band was less than 1%, and the below and above band blocking was less than 0.1%. All of the filter requirements were met over the temperature range of 77K to room ambient. We also discuss the results achieved in extending the above approach to the design and manufacture of a quadruple bandpass filter (with passbands centered at 1.23, 1.6, 2.2, and 3.75μm).

Small size and low weight are among the main drivers in modern military hand-held applications. Consequently, design-ers of such systems strive for combining multiple optical and electronic functions into the same piece of hardware. Present paper deals with the partial integration of an eye safe laser rangefinder into an optical channel for uncooled thermal imager using UMICORE's GASIR® optics. GASIR® is a chalcogenide glass with a transmission window from 0.8-15 µm, making it an effective material for use in near infrared, mid-wave infrared and far infrared applications. Due to the fact that uncooled sensors in the LWIR spectral band require optics with low f/numbers and that laser range-finders typically need a larger receiver aperture - in order to comply with the maximum range requirement - this ap-proach at first sight promises favorable synergies. However, it soon turns out that such a dual band approach makes life for the rangefinder part of the job difficult - by imposing special surface types required for achieving optical specifica-tions of the thermal channel, which may deteriorate the beam quality of the laser light as well as by introducing special coatings with potentially insufficient transmission at the specific laser wavelength. Several design versions have been developed and evaluated with the purpose of finding optimal balance between image quality of the thermal channel and the laser rangefinder performance. In this paper various optical and coating design aspects will be addressed together with the limitations of such a multi-spectral approach.

MCT was discovered in the UK in 1958. This paper reviews key developments in the research and development of the material and devices from the early days to the present. The growth of the material by Bridgman, LPE and MOVPE methods is described. Fabrication techniques are described for SPRITES, two dimensional and long linear "loophole" diode arrays and the more recent wafer scale technologies for very large arrays. The use of multilayer heterostructures in Auger-suppressed diodes, two-colour detectors and negative luminescence devices is outlined. A brief glimpse of the future potential for the growth of MCT directly onto silicon circuits is given.

France has a long and fruitful history regarding Mercury Cadmium Telluride (MCT) research and production and is still one of the leading countries for the production of MCT IR detectors. To give a historical account of its development and progress, SAGEM Défense Sécurité will describe the early days of MCT developments in France. CEA-Leti (the French Atomic Energy Commission and a leading applied research center in electronics) will then present the research carried out on second- and third-generation MCT technologies, followed by Sofradir who will discuss the production of these new detector types.

The first HgCdTe (MCT) activities at AEG-Telefunken in Germany were started in 1976. As part of the closing of AEG, the Heilbronn based IR-technology division was established as a spin-off company in 1995, under the brand name of AIM Infrarot-Module GmbH. A rapidly growing team of scientists focused on the detector-dewar-cooler technology and the development of linear photoconductive MCT arrays by applying the solid-state-recrystallization (SSR) technique for MCT growth, depositing and thinning MCT on sapphire substrates and oxide passivation. In 1979, after successful development of an own MCT-technology base, AEG-Telefunken entered into a license agreement with Texas Instruments for US Common Module (CM) technology in order to speed up the entry into full scale production with a transfer of MCT-material, dewar and cooler processes. CMs are still manufactured in small numbers. At the same time, a proprietary pc-MCT technology, independent of the CM production line, was developed and continuously matured and is today successfully applied in various custom designs like detectors for smart ammunition, for commercial and space applications. In 1982 started the development of 2nd Gen. photovoltaic MCT detectors, based on liquid-phase-epitaxy (LPE) in tilting and dipping technique and on planar array technology with Hg-Diffusion and ion implantation for pn-junction formation and CdTe/ZnS passivation. Linear MCT arrays in the 8-10,5 μm wavelength range with state of the art electro-optical performance have rapidly been demonstrated. Within the frame of the European anti-tank program TRIGAT, a two-way know-how-transfer between AEGTelefunken and SOFRADIR was established for linear LW MCT array processing, flip-chip-technology and dewar technology. Today, AIM's 2^nd Gen. portfolio is based on MCT-LPE in dipping technique on CdZnTe substrates, characterized by a very low defect and dislocation density for 0,9 μm to 15μm wavelength application. Array processing is performed by planar technique, Boron ion implantation, CdTe/ZnS passivation and intrinsic or extrinsic doping, respectively. Infrared systems with AIM's linear and 2-dim. Focal-Phase-Arrays are used in many state of the art programs in Germany and internationally for surveillance and targeting, seeker head systems or for spaceborne applications like e.g. hyperspectral imaging. AIM's current MCT developments include for example MW/LW-MBE-MCT layers and array processing for 3^rd Gen. detectors, avalanche NIR-MCT photodiodes for low background application, MBE on 4" alternative substrates and 2- dim. arrays with very long 15μm cut-off for space-based application to meet the future demands of IR-systems.

MCT was independently synthesized in Soviet Union one year later than in UK. MCT investigations and technology development virtually started from the material origin. Main milestones of this way from early days to the present are reviewed. Deep researches and MCT based device development spring from the projects which Scientific Research Institute of Applied Physics (now ORION Research and Production Association) charged with in 1969. Gradual material, photoresistor and photodiode technology developments were carried out in 1970-1990 and resulted in n-type single crystals MCT industrial production mastery, photoconductive detectors series up to 200 elements and high frequency heterodyne detectors production. New generation devices - focal plane arrays and MCT epitaxial technology were developed in 1980-2000. MCT FPA and heteroepitaxial technology enhancement since 2000 led to production of the family of long linear and staring second generation arrays in various formats and package configurations. Third generation devices pointed on advanced MCT heteroepitaxial technologies and new type photosensitive structures creation are under development. Original investigations of some interesting phenomena in MCT and device structures such as injection heat transfer and negative differential conductance in MCT diodes, metal-tunnel transparent insulator structures are also presented.

The purpose of this paper is to review the main achievements in the investigations of HgTe-based ternary alloys and point out the Polish contributions in development of the middle and long wavelength infrared photodetectors. Research and development efforts in Poland were concentrated mostly on uncooled market niche. At the beginning, a modified isothermal vapor phase epitaxy has been used for research and commercial fabrication of photoconductive, photoelectromagnetic, and other HgCdTe devices. Bulk growth and liquid phase epitaxy were also used. Recently, the fabrication of infrared devices relies on low temperature epitaxial technique, namely metalorganic vapor phase deposition. At present stage of development, the photoconductive and photoelectromagnetic (PEM) detectors are gradually replaced with photovoltaic devices which offer inherent advantages of no electric or magnetic bias, no heat load and no flicker noise. Potentially, photodiodes offer high performance and very fast response. However, conventional photovoltaic uncooled detectors suffer from low quantum efficiency and very low junction resistance. The problems have been solved with advanced band gap engineered architecture, multiple cell heterojunction devices connected in series, and monolithic integration of the detectors with microoptics. In final part of the paper, the Polish achievements in technology and performance of HgMnTe and HgZnTe photodetectors are presented.

We delineate and discuss the more significant developments in the corporate and DOD funded (Hg,Cd)Te program initiated and conducted at the Honeywell Research Center, located in Minneapolis, MN. This includes a discussion of the candidate materials initially investigated, the selection process and the basis for the decision to pursue the development of the ternary (Hg,Cd)Te. We describe the various growth approaches investigated, present the results and discuss the challenges. The integrated investigation included an intensive materials study and the evaluation of the electrical, mechanical, optical and sensor properties of this material. These developments contributed to making (Hg,Cd)Te the dominant long wavelength sensor material.

This paper describes the history and current status of HgCdTe infrared detector technology at BAE Systems in Lexington, Massachusetts, whose corporate legacy includes Honeywell (1962-1991), Loral (1991-1996), and Lockheed Martin (1996-2000). The Honeywell Radiation Center was founded in 1962 in Boston, Massachusetts. Shortly thereafter, primitive HgCdTe samples began to arrive from the Honeywell Corporate Research Center in Hopkins, Minnesota for evaluation as possible IR detectors. In 1967, procedures for the growth of HgCdTe inhomogeneous large-grain-polycrystalline ingots by a modified Bridgman method were transferred from the Research Center to the Radiation Center. In 1968 the Radiation Center moved to new facilities in Lexington, Massachusetts. HgCdTe activities have expanded and evolved in the ensuing years, remaining in the Lexington, Massachusetts facilities up to the present. This paper reviews the role that the Honeywell/Loral/Lockheed Martin/BAE Systems facility in Lexington, Massachusetts has played in the success of HgCdTe as today's preeminent, highest performance, most versatile, and most widely applicable infrared detector material for the 1-30 μm spectral range. We examine the evolution of both photoconductive and photovoltaic HgCdTe detectors from early unpassivated ill-understood single-element devices through production of linear arrays and to today's large-format two-dimensional IR Focal Plane Arrays for the most demanding spaceborne applications. We examine the progress made in HgCdTe materials science and technology, including improved highly-homogeneous bulk crystal growth, liquid phase epitaxy and metalorganic vapor phase epitaxy. Various devices are used to illustrate the evolution of HgCdTe technology, including the n-type photoconductor, the trapping-mode photoconductor, and the two-layer LPE P-on-n heterojunction.

Work on HgCdTe began at Texas Instruments in the early 1960s, and continued through 1997 when TI's defense business was sold first to Raytheon, and subsequently in 1998 to DRS Technologies. This presentation traces the history of HgCdTe's evolution throughout this timeframe to the present day, as viewed through the eyes of the author and several of his TI contemporaries who have survived the experience. The materials technology will be traced from the early days of bulk growth by the solid state recrystalization technique, through the traveling heater method of growth, to liquid phase epitaxy from large Te-rich melts, to vapor phase growth by molecular beam epitaxy and metal organic chemical vapor deposition. The evolution of detector device architectures at TI over the years will be discussed, from the early, successful days of photoconductors and the Common Module System, through the somewhat problematic and relatively unsuccessful foray into charge coupled and charge injection devices for 2^nd generation FPAs for the Javelin program, to the outstandingly successful development of the vertically integrated photodiode (VIP) and high density VIP FPA architectures for mono-color and multi-color 3^rd generation systems. The versatile, and unique nature of this infrared semiconductor materials system will be highlighted by reference to current work at DRS Technologies into electron avalanche photodiodes (EAPDs), for use in active/passive IR systems, and high operating temperature (HOT) detectors, which threaten to eventually offer BLIP photon detection at uncooled operating temperatures, over the whole IR spectrum from 1 to 12um.

This paper reviews the historical progress of HgCdTe material and device development at Raytheon Vision Systems starting with the initial work in 1965 at what was then the Santa Barbara Research Center, a subsidiary of the Hughes Aircraft Company and progressing up to the present time. Because of the long history, all the details cannot be presented in a single paper; instead, we focus only on a few major accomplishments. In HgCdTe material preparation these include: the early bulk single crystal growth methods; the advent of liquid phase epitaxial growth from Hg melts; and, the most recent molecular beam epitaxial methods. For IR photodetector devices, we started with just single element detectors operating either in photoconductive or photovoltaic mode, then progressed to multi-element linear arrays, then to 2-D arrays on Si read-out circuits and, finally to the very large focal plane (>2k × 2k), dual-band, and APD arrays of today. Some applications of these devices in IR systems will be presented. Technical issues will be discussed only to the extent necessary to support the historical narrative. Some interesting anecdotes will be included.

Since the late '60's Teledyne Imaging Sensors (TIS-formerly Rockwell Science Center) has developed IR sensor technology and produced IR sensors for both military and commercial applications. In the late '70's, after excursions into the Pb-salts and InAsSb alloys, TIS began to study HgCdTe and has pursued this materials system aggressively ever since. Beginning with Te-corner liquid phase epitaxy (LPE) by dipping, tipping, and sliding, Teledyne migrated through metal organic chemical vapor deposition (MOCVD)-a very challenging growth technique-to molecular beam epitaxy (MBE), where we have found a reliable and flexible technique suited to the most advanced architectures. We used substrates from Cd(Zn)Te to sapphire, GaAs, and silicon. Ion implantation and planar diode architectures have allowed high density device geometries exploited in our double layer planar heterostructure (DLPH) single color diodes and our simultaneous multispectral integrated technology (SUMIT) two color diodes. The performance of these devices equals or exceeds that of all baseline MCT devices reported by other techniques. These devices have dark currents that are readily characterized over 13 orders of magnitude by a simple heuristic, "Rule 07," for a wide range of temperature and wavelength.

The study of HgCdTe technology in Israel began in the mid 1970's under the leadership of the late Prof. Kidron and his group at the Technion, Israel Institute of Technology. The R&D efforts were continued by other groups at the Technion and other universities and research institutes in Israel, as well as by SCD. Many aspects of the technology of this material were studied, including both bulk crystal and epitaxial growths and microelectronic fabrication methods, with an emphasis on surface treatment and passivation. Various characterization methods were developed to study both the basic and applied material and device properties. The efforts, reviewed in this article, matured at SCD as it commercialized the HgCdTe technology, launching large-volume production lines of state-of-the-art linear and multi-linear TDI LWIR detector arrays of various sizes from 10×1 to 480×6 elements. Over the years, SCD has supplied its customers with thousands of both photoconductive (PC) and photovoltaic (PV) detectors, which are briefly presented in the paper.

The authors summarize the past 40-years history on the development of HgCdTe infrared detectors in Japan. At the early stage of development of material growth, high-quality HgCdTe layers were obtained by liquid phase epitaxy technique, owing to lattice-matched CdZnTe substrates. Hetero-epitaxial growth techniques of HgCdTe were also successfully developed to obtain epilayers on much larger and cheaper substrates such as GaAs and Si, using methods of metal-organic chemical vapor deposition and molecular beam epitaxy, where key issues were controlling surface orientation, surface polarity and so forth. Fabrication process of p-on-n junction photodiodes was developed with various improvements on ion implantation and surface passivation. On the basis of technologies mentioned above, large-scale infrared focal plane arrays were realized with superior thermal images.

This paper reviews the development history and current status of HgCdTe based IR detector of which the study had started from 1980's in South Korea. It covers the fields from single element diode to 2-dimensional IR detector as well as dewar technology. The past studies of large area single element diode, linear array detector, 2-D IRFPAs are reported which include HgCdTe diode array, ROIC and hybridization technologies. Thanks to the sound cooperation between academia, research institute, industry, and government, current progress of 2-D IR detector shows high performance and reliability to be able to be utilized in fields. Finally, prospective future of IR detector in Korea is addressed.

The history and milestones of HgCdTe infrared detector technology in China has been reviewed, including the material growth, device processing and design. It is also presented that the HgCdTe infrared detector has been used well in space remote sensing technology. The current status of HgCdTe technology is focused on focal-plane arrays (FPAs) fabricated with HgCdTe grown on different substrate, including GaAs and Si substrate, by epitaxy method. The FPA imaging, material growth process and interface engineering have been discussed.

In this paper a brief history of HgCdTe based research and development in Australia is presented. It describes some of the motivation behind decisions made in Australia related to the HgCdTe international research effort, the early stages of development of HgCdTe materials and device research in Australia, and main research activities in Australia over a period of twenty five years. Also presented are some of the major achievements and inevitable failures.

In the present paper, we describe the development of Long Wave Infrared (8-12 μm) linear and 2-D IR FPA detectors using HgCdTe for use in thermal imagers and IIR seekers. In this direction, Solid State Physics Laboratory(SSPL) (DRDO) tried to concentrate initially in the bulk growth and characterization of HgCdTe during the early eighties. Some efforts were then made to develop a LWIR photoconductive type MCT array in linear configuration with the IRFPA processed on bulk MCT crystals grown in the laboratory. Non availability of quality epilayers with the required specification followed by the denial of supply of CdTe, CdZnTe and even high purity Te by advanced countries, forced us to shift our efforts during early nineties towards development of 60 element PC IR detectors. High performance linear PC arrays were developed. A novel horizontal casting procedure was evolved for growing high quality bulk material using solid state recrystallization technique. Efforts for ultra purification of Te to 7N purity with the help of a sister concern has made it possible to have this material indigenously. Having succeded in the technology for growing single crystalline CdZnTe with (111) orientation and LPE growth of HgCdTe epilayers on CdZnTe substrates an attempt was made to establish the fabrication of 2D short PV arrays showing significant IR response. Thus a detailed technological knowhow for passivation, metallization, ion implanted junction formation, etc. was generated. Parallel work on the development of a matching CCD Mux readout in silicon by Semiconductor Complex Limited was also completed which was tested first in stand-alone mode followed by integration with IRFPAs through indigenously-developed indium bumps. These devices were integrated into an indigenously fabricated glass dewar cooled by a self-developed JT minicooler. In recent years, the LPE (Liquid Phase Epitaxy) growth from Terich route has been standardized for producing epitaxial layers with high compositional and thickness uniformity leading to a respectable stage of maturity in FPA technology.

Range-gated viewing is a prominent technique for night vision, remote sensing and vision trough obstacles (fog, smoke, camouflage netting ). Furthermore, range-gated images reflect not only the scene reflectance but also contain depth information. The whole depth information can be calculated from a minimum number of two range-gated images via the super-resolution depth mapping technique. For the first time, this method is applied to range-gated viewing at infrared wavelengths. An EBCMOS camera and a solid sate laser illumination in the 1.5 μm wavelength scale were used to depth-map a scene with minimal laser activity of 9 ns per image.

New applications require high sensitivity infrared (IR) sensors in order to detect very low incident fluxes. Laser gated imaging has, in particular, additional specific needs. IR sensors for this type of application are synchronized with eye-safe lasers, and have to detect a weak signal backscattered from the target on the order of 10 photons per pulse. They also have to be able to operate with a very short integration time, typically one hundred nanoseconds, to gate the backscattered signal around the target. In partnership with Sofradir, CEA/LETI (France) has developed high quality HgCdTe avalanche photodiodes satisfying these requirements. In parallel, specific studies have been carried out at the Read-Out Circuit level to develop optimized architectures. Thanks to these advances, a new Integrated Dewar Detector Cooler Assembly has been developed. This new product is the first step in a road-map to address low flux infrared sensors in the next few years.

The optimization of HgCdTe avalanche-photo-diodes (e-APD) and focal plane arrays (FPA) are reported. The gain performances was measured in planar homo-junction APDs with Cd compositions between x_Cd=0.3 to 0.41. Exponentially increasing gain, synonym of exclusive electron multiplication, was observed in all the devices up to M>100. The high gain at high x_Cd opens the path to thermo-electric cooled active imaging at T=200K. This perspective is corroborated by the demonstration of high gains and low excess noise factor F=1.2 in extrinsically doped MW-APDs, which enables reduced dark-current at high temperatures. The equivalent input dark current (Ieq_in) decreased from 200 fA to 1 fA, when the cut-off wavelength was reduced from λ _c=5.2 μm to 4.1 μm at M=100 and T=80 K. This shows that sensitivity can be optimized by increasing xCd, at the cost of increased reverse bias. A new horizontal-gain-well (HGW) hetero-structure was processed to optimize the sensitivity at high gain and low bias. The first HGW-APDs had gains comparables with MW e-APDs and 50 times lower dark-current at T=200 K. They did also display surprisingly high quantum efficiency in the MWIR range, η_peak=30%, which enables thermal imaging at high operating temperature. The high performance of MW-APDs was confirmed by the characterizations of a first 320x256 30μm pitch APD-FPA, yielding a 99.8 % operability, low gain dispersion (<10%) and low noise equivalent photons (NEPh=3 at t_int=1 μs) for gains up to M=70. The maturity of the DEFIR HgCdTe e-APD-FPA technology was highlighted by the first demonstration of passive amplified imaging.

This paper is a theoretical analysis and a comparison of imaging sensor technologies compatible with active imaging applications that operate in the SWIR band. Two types of sensors are commonly used: detectors with gain induced by internal photoelectron multiplication process (HgCdTe APD FPA and InGaAs/InP TE EBCMOS) and detectors without internal gain (InGaAs FPA). Active imaging requires a sensitive high-speed sensor able to detect a short, weak pulse backscattered from a target. The goal is to reach a sensitivity defined by a NEPh of 10 photons rms, and a SNR of 5-10 for an input signal of 100-200 photons/pulse/pixel. We demonstrate that the HgCdTe APD FPA detector with gain is intrinsically the best technology to fulfill the aforementioned requirements. In comparison, the InGaAs/InP TE EBCMOS also works well but suffers from limited quantum efficiency, less than 30% at the most. The main advantage of detectors with internal gain is their potential to amplify the laser signal above the readout noise level, under the condition that the excess noise factor induced by the multiplication process remains close to 1. The InGaAs FPA detector without gain is lower cost, however it exhibits a NEPh of around one order of magnitude higher and a SNR 3 to 6 times lower. At a system level, a more powerful laser will compensate for this difference but will also increase the cost. In conclusion to the tradeoff regarding performance versus cost, each specific system need should determine the best matched technology.

In this work, we present the study on In_0.53Ga_0.47As/GaAs_0.51Sb_0.49 type-II heterojunction PIN diodes and Separate Absorption, Charge and Multiplication (SACM) APDs utilising In_0.52A_l0.48As as the multiplication layer and In_0.53Ga_0.47As/GaAs_0.51Sb_0.49 type-II heterostructures as the absorption layer. In_0.52Al_0.48As lattice matched to InP has been shown to have superior excess noise characteristics and multiplication with relatively low temperature dependence compared to InP. Furthermore, the type-II staggered band line-up leads to a narrower effective bandgap of approximately 0.49 eV corresponding to the APD cut off wavelength of 2.4 μm. The device exhibited low dark current densities near breakdown. The device also exhibited multiplication in excess of 100 at 200 K.

The operation of the mid-wave infrared (MWIR) HgCdTe cylindrical electron injection avalanche photodiode (e-APD) is described. The measured gain and excess noise factor are related to the to the collection region fill factor. A 2D diffusion model calculates the time dependent response and steady state pixel point spread function for cylindrical diodes, and predicts bandwidths near 1 GHz for small geometries. A 2 μm diameter spot scan system was developed for point spread function and crosstalk measurements at 80 K. An electron diffusion length of 13.4 μm was extracted from spot scan data. Bandwidth data are shown that indicate bandwidths in excess of 300 MHz for small unit cells geometries. Dark current data, at high gain levels, indicate an effective gain normalized dark density count as low as 1000 counts per μs per cm2 at an APD gain of 444. A junction doping profile was determined from capacitance-voltage data. Spectral response data shows a gain independent characteristic.

Near-infra-red sensing with silicon is limited by the bandgap of silicon, corresponding to a maximum wavelength of absorption of 1.1 μm. A new type of CMOS sensor is presented, which uses a SiGeC epitaxial film in conjunction with novel device architecture to extend absorption into the infra-red. The SiGeC film composition and thickness determine the spectrum of absorption; in particular for SiGeC superlattices, the layer ordering to create pseudo direct bandgaps is the critical parameter. In this new device architecture, the p-type SiGeC film is grown on an active region surrounded by STI, linked to the S/D region of an adjacent NMOS, under the STI by a floating N-Well. On a n-type active, a P-I-N device is formed, and on a p-type active, a P-I-P device is formed, each sensing different regions of the spectrum. The SiGeC films can be biased for avalanche operation, as the required vertical electric field is confined to the region near the heterojunction interface, thereby not affecting the gate oxide of the adjacent NMOS. With suitable heterojunction and doping profiles, the avalanche region can also be bandgap engineered, allowing for avalanche breakdown voltages that are compatible with CMOS devices.

We report on the characterisation of impact ionisation in InAs and the development of practical InAs avalanche photodiodes (APDs) to exploit the properties identified. Avalanche multiplication measurements show that the hole ionisation coefficient is negligible in InAs. We have demonstrated that this results in extremely low excess multiplication noise, F<2, for electron initiated gain. Indeed the excess noise measured was comparable to the excellent results reported for HgCdTe APDs and notably lower than those reported for other III-V based APDs. It could be desirable to exploit this extremely low excess noise characteristic, now demonstrated in a III-V material, in a number of applications. In this work we consider in particular the exploitation in an InAs APD focal plane array, to achieve enhanced sensitivity imaging in the SWIR. The greatest barrier to such exploitation is the requirement to sufficiently suppress the reverse leakage current, typically present in InAs diodes under high reverse bias at room temperature. We report on initial developments in this respect, presenting leakage current results for the temperature ranges accessible by both thermoelectric and Stirling engine cooling. These demonstrate that InAs APDs have the potential to operate at higher temperatures than the sMWIR sensitive composition of HgCdTe currently used in emerging APD focal plane array applications. We also show that InAs APDs are capable of operating at bias voltages below 10V, supporting easy integration with fine pitch read out ICs, without band to band tunnelling contributing significantly to the leakage current, even at low operating temperatures.

The increasing demand for short wave infrared (SWIR) imaging technology for soldier-based and unmanned platforms requires camera systems where size, weight and power consumption are minimized without loss of performance. Goodrich, Sensors Unlimited Inc. reports on the development of a novel focal plane (FPA) array for DARPA's MISI (Micro-Sensors for Imaging) Program. This large format (1280 x 1024) array is optimized for day/night imaging in the wavelength region from 0.4 μm to 1.7 μm and consists of an InGaAs detector bump bonded to a capacitance transimpedance amplifier (CTIA)-based readout integrated circuit (ROIC) on a compact 15 μm pixel pitch. Two selectable integration capacitors provide for high dynamic range with low (< 50 electrons) noise, and expanded onchip ROIC functionality includes analog-to-digital conversion and temperature sensing. The combination of high quality, low dark current InGaAs with temperature-parameterized non-uniformity correction allows operation at ambient temperatures while eliminating the need for thermoelectric cooling. The resulting lightweight, low power implementation is suitable for man-portable and UAV-mounted applications.

SiGe based Focal Plane Arrays offer a low cost alternative for developing visible- NIR focal plane arrays that will cover the spectral band from 0.4 to 1.6 microns. The attractive features of SiGe based IRFPA's will take advantage of Silicon based technology, that promises small feature size, low dark current and compatibility with the low power silicon CMOS circuits for signal processing. This paper discusses performance comparison for the SiGe based VIS-NIR Sensor with performance characteristics of InGaAs, InSb, and HgCdTe based IRFPA's. Various approaches including device designs are discussed for reducing the dark current in SiGe detector arrays; these include Superlattice, Quantum dot and Buried junction designs that have the potential of reducing the dark current by several orders of magnitude. The paper also discusses approaches to reduce the leakage current for small detector size and fabrication techniques. In addition several innovative approaches that have the potential of increasing the spectral response to 1.8 microns and beyond.

Raytheon Vision Systems (RVS) has obtained the initial performance data on a 1280x1024 format short wave infrared (SWIR) sensor with a dark current of 1 nA/cm² and low noise input circuit of five noise electrons (5 e-), which is 2× lower electronic read-out noise and 2× lower dark current than previous designs. A remarkable feature of the sensor is that a novel high dynamic range circuit is also designed into the 15 × 15 μm pixel unit cell, in a large format, high density 1280×1024 SWIR FPA. The integration of the conflicting design requirements of extremely low noise with high dynamic range allows recognition of low contrast targets, without saturation from bright sources within the same frame of information. This enables operation in urban environments at low levels of ambient illumination, and simultaneously with bright sources that saturate conventional sensors.

Aerius Photonics has developed large InGaAs arrays (1K x 1K and greater) with low dark currents for use in night vision applications in the SWIR regime. Aerius will present results of experiments to reduce the dark current density of their InGaAs detector arrays. By varying device designs and passivations, Aerius has achieved a dark current density below 1.0 nA/cm² at 280K on small-pixel, detector arrays. Data is shown for both test structures and focal plane arrays. In addition, data from cryogenically cooled InGaAs arrays will be shown for astronomy applications.

The InfraRed staring arrays developed by SOFRADIR are more and more compact and offer system solutions for wide range of IR wavebands. IR detectors have been taken to an even more advanced level of sophistication to achieve staring arrays high performances. Latest developments have also been focused on the silicon readout circuit. Digital conversion on chip is one of the recent progresses in this field of activity. In order to match each system requirements, on chip high performance ultra low power ADCs have been developed. Beyond the performance aspects, digital focal plane arrays can be considered as the first step towards low cost Dewar family, since they allow for a more simple electrical interface on Dewar designs and on chip image processing. Recent results concerning these new readout circuit architectures are presented in this paper.

Over the recent 25 years Ricor has fielded in excess of 50,000 Stirling cryocoolers, among which approximately 30,000 units are of micro integral rotary driven type. The statistical population of the fielded units is counted in thousands/ hundreds per application category. In contrast to MTTF values as gathered and presented based on standard reliability demonstration tests, where the failure of the weakest component dictates the end of product life, in the case of field reliability, where design and workmanship failures are counted and considered, the values are usually reported in number of failures per million hours of operation. These values are important and relevant to the prediction of service capabilities and plan.

Infrared sensors play a critical role in detection, guidance, and targeting in today's military systems and warfighter equipment, ranging from man-portable to space-borne. Although significant progress is being made in the development of IR imagers, another important component of IR sensors has not evolved significantly-the optics. Current IR lenses are primarily made of expensive single-crystal germanium with tedious mechanical fabrication operations that include grinding, polishing, and edging. There is an industry wide need for lower cost and higher performance IR lenses. Agiltron has developed a technology to directly mold IR lenses to net-shape without additional finishing operations. This manufacturing technology produces optics with many-fold reductions in cost, size, weight, and fabrication time. The ability to reproducibly manufacture aspheric optics with complex net-shapes reduces the number of lenses traditionally required for imaging systems, providing aberration correction as well as system weight and size reductions. Additionally, anti-reflective surfaces can be molded into the glass, eliminating the need for expensive AR coatings. This technology utilizes a new chalcogenide glass material that reduces temperature induced index of refraction changes to near zero, and has a thermal expansion coefficient similar to aluminum. The result is a new generation of low cost, high performance and thermally robust IR lens systems.

Over the last decade, SCD has developed and manufactured high quality InSb Focal Plane Arrays (FPAs), which are currently used in many applications worldwide. SCD's production line includes many different types of InSb FPA with formats of 320x256, 480x384 and 640x512 elements and with pitch sizes in the range of 15 to 30 μm. All these FPAs are available in various packaging configurations, including fully integrated Detector-Dewar-Cooler Assemblies (DDCA) with either closed-cycle Sterling or open-loop Joule-Thomson coolers. With an increasing need for higher resolution, SCD has recently developed a new large format 2-D InSb detector with 1280x1024 elements and a pixel size of 15μm. The InSb 15μm pixel technology has already been proven at SCD with the "Pelican" detector (640x512 elements), which was introduced at the Orlando conference in 2006. A new signal processor was developed at SCD for use in this mega-pixel detector. This Readout Integrated Circuit (ROIC) is designed for, and manufactured with, 0.18 μm CMOS technology. The migration from 0.5 to 0.18 μm CMOS technology supports SCD's roadmap for the reduction of pixel size and power consumption and is in line with the increasing demand for improved performance and on-chip functionality. Consequently, the new ROIC maintains the same level of performance and functionality with a 15 μm pitch, as exists in our 20 μm-pitch ROICs based on 0.5μm CMOS technology. Similar to Sebastian (SCD ROIC with A/D on chip), this signal processor also includes A/D converters on the chip and demonstrates the same level of performance, but with reduced power consumption. The pixel readout rate has been increased up to 160 MHz in order to support a high frame rate, resulting in 120 Hz operation with a window of 1024×1024 elements at ~130 mW. These A/D converters on chip save the need for using 16 A/D channels on board (in the case of an analog ROIC) which would operate at 10 MHz and consume about 8Watts A Dewar has been designed with a stiffened detector support to withstand harsh environmental conditions with a minimal contribution to the heat load of the detector. The combination of the 0.18μm-based low power CMOS technology for the ROIC and the stiffening of the detector support within the Dewar has enabled the use of the Ricor K508 cryo-cooler (0.5 W). This has created a high-resolution detector in a very compact package. In this paper we present the basic concept of the new detector. We will describe its construction and will present electrical and radiometric characterization results.

We show design, modeling, fabrication, and characterization results for high-transmission broad-angle frequency selective surfaces (FSSs) in the mid-infrared. The single metal layer of a FSS allows its incorporation directly into focal plane array (FPA) designs, thus allowing direct integration of the filtering and polarizing properties of the FSS into sensors from single photodetectors to FPAs. In thin film filter designs the number of layers and film thicknesses may vary pixel-to-pixel, making fabrication difficult. In contrast, changes in spectral passband or polarization state are easily accomplished with changes to the FSS pattern. We have designed, fabricated, and tested FSSs of patterned gold on a GaAs substrate. Designs include single metal layers and a metal plus a dielectric layer. Design and modeling were performed using rigorous coupled wave analysis (RCWA). Further simulations were performed using a 3D Helmholtz code. All simulations account for the loss and dispersion of the metal at these wavelengths. FSSs with narrowband and broadband capabilities and for polarizing and non-polarizing applications were designed. We will show measured results of both reflection and transmission over a broad spectral (covering all of the mid and thermal infrared) and angular (near normal to near grazing) range. These measurements compare favorably with the modeled results.

This paper presents analysis of digital images from single and dual sensor systems of man and vehicle size targets at low light conditions (at or below starlight conditions, 10-4 foot candles). More specifically, the image analysis will focus on measurement and interpretation of localized signal to noise ratio (LSNR) from these targets and connection to target contrast and spatial range. First, this paper will define localized signal to noise ratio and its context to information rich and poor targets to various background scenes. Then this definition will be applied to an artificially generated target to background scene composed of various gray scale square targets with various contrasts and Gaussian noise levels embedded on gray scale background with defined contrast and Gaussian noise level. The next section defines the field experiment and equipment setup to measure localized SNR for actual man and vehicle size targets in low light level conditions using a fused dual sensor system. Initial results of this field experiment shows line shape behavior of localized SNR is better represented by a decaying exponential function to spatial range likely related to Beer-Lambert Law of atmospheric radiation propagation. Finally, localized SNR is greater for fused dual sensor system as compared to its respective single sensor system modes for man and vehicle targets specified in this paper. Paper has been cleared by DOD/OSR for Public Release under OSR Ref: 07-S-1131 on April 16, 2007.

InGaAs is the material of preference for uncooled imaging in the [0.9-1.7 μm] SWIR range, as it can be manufactured on low cost InP substrates in a mainstream technology for optical telecommunications. By removing the substrate the spectral range can be extended to the [0.6 - 1.7 μm] range. In this way low cost, room temperature operated FPAs cameras for imaging and hyperspectral applications can be developed. The FPA is built around a low power CTIA stage with 3 S&H capacitors in the 20*20 um² unit cell. This approach results in a synchronous shutter operation, which will support both ITR and IWR operation. In IWR mode the integration dead time is limited to max. 10 μsec. The CDS operation yields in a high sensitivity combined with a low noise: This presentation will focus on the development of a 20 μm pitch 320*256 device, with the following main characteristics: 20 μV/e-sensitivity and < 60 e-noise. The 4 low-power, differential outputs are enabling to drive an output load of > 30 pF at 40 Msamples/sec each, resulting in a > 1700 Hz frame rate, while at the same time the overall nominal power dissipation is < 200 mW. The ROIC is realized in a 0.35 um technology and the outputs are designed to drive directly a 3.3 V, 1.5 V VCM differential AD convertor. The circuit also supports a NDR operating mode to further reduce the noise of the FPA. A small from factor camera with Cameralink output is built around this FPA.

GaSb substrates have advantages that make them attractive for implementation of a wide range of infrared (IR) detectors with higher operating temperatures for stealth and space based applications. A significant aspect that would enable widespread commercial application of GaSb wafers for very long wavelength IR (VLWIR) applications is the capability for transmissivity beyond 15 μm. Due largely to the GaSb (antisite) defect and other point defects in undoped GaSb substrates, intrinsic GaSb is still slightly p-type and strongly absorbs in the VLWIR. This requires backside thinning of the GaSb substrate for IR transmissivity. An extremely low n-type GaSb substrate is preferred to eliminate thinning and provide a substrate solution for backside illuminated VLWIR devices. By providing a more homogeneous radial distribution of the melt solute to suppress GaSb formation and controlling the cooling rate, ultra low doped n:GaSb has been achieved. This study examines the surface properties and IR transmission spectra of ultra low doped GaSb substrates at both room and low temperatures. Atomic force microscopy (AFM), homoepitaxy by MBE, and infrared Fourier transform (FTIR) analysis was implemented to examine material quality. As compared with standard low doped GaSb, the ultra low doped substrates show over 50% transmission and consistent wavelength transparency past 23 μm with improved %T at low temperature. Homoepitaxy and AFM results indicate the ultra low doped GaSb has a low thermal desorbtion character and qualified morphology. In summary, improvements in room temperature IR transmission and extended wavelength characteristics have been shown consistently for ultra low doped n:GaSb substrates.

The spatial and temporal characteristics of fire are of great concern to fire suppression managers. This information is critical when deciding what resources to bring and where to put them. The ability to acquire spatially explicit data on active fires is of great importance for the protection of personnel, property, and resources. The purpose of this paper is to investigate the extraction of fire characteristics using hyperspectral, LiDAR and multispectral thermal remote-sensing systems. This will be achieved through: (1) a discussion of acquisition and image-processing techniques of remotely sensed infrared data that improves tactical awareness during both small and large-scale regional fire disturbances; (2) the improvement of baseline data sources for fuel mapping and propagation modeling acquired from LiDAR and hyperspectral sources; and (3), the capabilities of Coherent Doppler LiDAR to monitor atmospheric conditions. The successful evolution of today's sensors with these capabilities in mind will produce more rapid decision-making and resource allocation for the fire mitigation community.

In case bird migration routes cross approach corridors near airports bird strike prevention with thermal imaging systems has advantages compared to others technologies i.e. RADAR systems. In our case a stereoscopic thermal imaging system sensitive in the mid wavelength range (3 - 5 μm) with high geometrical (640 × 512 pixel) and high thermal resolution (< 20 mK) measures in real time the swarm size, direction and velocity with high accuracy in order to give an early warning under all relevant weather conditions during day, night and twilight. The system is self-calibrating to keep the relative position of the paired stereoscopic thermal imagers in the sub-pixel range under all environmental conditions. The stereoscopic systems are placed in a sufficient distance to the crossing with the take-off or landing path to enable warning times of several minutes. Moreover the risk potential of the swarm is determined by taking the size of a single bird as well as the number of birds in the swarm into account. By using this information an arrival time of the swarm at the crossing point is determined and provided to the air security controllers together with the risk potential of the swarm.

A novel and low-cost technique of standoff detection is presented that permits the detection of explosives and other contraband substances that are hidden under clothing at standoff distances . The technique uses NIR beams of wavelengths found in ordinary domestic remote controls, combined with various signal recovery techniques commonly used in astronomy. This alternative technique, whilst sophisticated, utilises readily available optoelectronic components. It is inherently far more portable than currently available commercial alternatives and is easy to use. A pre-production prototype successfully detected and identified the common homemade explosives, ammonium nitrate and hydrogen peroxide, which were concealed behind clothing from a distance of 5 metres under daytime conditions. In principle, this distance could be extended as far as 50 metres without a significant increase in cost or complexity. Another advantage of this device is that apart from providing standoff chemical signatures and analyses of concealed substances, this it can simultaneously superimpose the chemical information on top of a normal TV image in a data fusion approach; that is, an image appears on the screen , the area/subject of interest can be zoomed in on and enlarged and a representation of a chemical spectrum appears on the screen underneath the image. A supplemental technique is also reported upon that, under the appropriate circumstances, enable actual imaging of concealed objects to be accomplished.

Emerging dual-camera dual-band (DCDB) infrared camera systems are playing an increasing role in temperature estimation and range measurement. This paper discusses the optimal design of a DCDB imaging system that makes use of contemporary filter fabrication technologies and improving detector performance. A two-color stereographic system allows for the temperatures of the objects to be measured without assuming a priori knowledge of emissivities, as well as providing a basis for estimating the distances to the objects. Multiple system design approaches are compared and key elements of the design trade space are described, including the selection of camera separation distance and specific infrared passbands. Analytical support for the methodology is provided by analyzing data from simulated infrared scenes. Finally, data from a laboratory-based DCDB system are analyzed and compared with model predictions.

Often it is necessary to track moving objects on horizontal paths. Human error and the associated cost and dangers of using humans lead to a requirement to automate this task. The system presented here was designed, built and tested. The system uses an IR beacon and a microcontroller receiver/controller module. The design consists of a field programmable gate array (FPGA) based IR transmitter and a microcontroller based IR receiver/controller. The design consisted of two main parts, the transmitter (beacon) and the receiver/controller module. The receiver was implemented with a FPGA so that the characteristics of the beacon signal could be adjusted more quickly and with greater precision. The controller module was integrated with the receivers and detailed system integration tests were performed. Measurements were collected, recorded and analyzed.

Sensitive and fast detection of explosives remains a challenge in many threat scenarios. Fraunhofer IPM works on two different detection methods using mid-infrared absorption spectroscopy in combination with quantum cascade lasers (QCL). 1. stand-off detection for a spatial distance of several meters and 2. contactless extractive sampling for short distance applications. The extractive method is based on a hollow fiber that works as gas cell and optical waveguide for the QCL light. The samples are membranes contaminated with the explosives and real background. The low vapor pressure of TNT requires a thermal desorbtion to introduce gaseous TNT and TATP into the heated fiber. The advantage of the hollow fiber setup is the resulting small sample volume. This enables a fast gas exchange rate and fast detection in the second range. The presented measurement setup achieves a detection limit of around 58 ng TNT and 26 ng TATP for 1 m hollow fiber. TATP - an explosive with a very high vapor pressure in comparison to TNT or other explosives - shows potential for an adequate concentration in gas phase under normal ambient conditions and thus the possibility of an explosive detection using open path absorption of TATP at 8 μm wavelength. In order to lower the cross sensitivities or interferents with substances with an absorption in the wavelength range of the TATP absorption the probe volume is checked synchronously by a second QCL emitting beside the target absorption wavelength. In laboratory measurements a detection limit of 5 ppm*m TATP are achieved.

Liquid explosives have been used in terrorism recently. Inspection of bottles becomes very important, because these liquid explosive or it raw materials can be carried by bottles easily. Hydrogen peroxide is typical raw materials of liquid explosives. It was difficult to evaluate concentration of hydrogen peroxide in the drink in the bottle, because of similarity of its optical properties to those of water. Using near infrared spectrum and multivariate statistical analysis, concentration of percent order of hydrogen peroxide in the bottle can be evaluated from outside of the bottle instantly. Hydrogen peroxide has been detected in not only a clear PET or glass bottle but also a colored glass bottle. Hydrogen peroxide mixed by soft drink such as coke or orange juice with pulp also detected by this method easily. This technique can be applied to inspection of a bottle at airport security so on.

We report on initial measurements of the low-temperature thermal properties of a device that is similar to the experimental apparatus used for absolute cryogenic radiometry (ACR) within the Low Background Infrared Radiometry (LBIR) facility at NIST. The device consists of a receiver cavity mechanically and thermally connected to a temperature-controlled stage through a thin-walled polyimide tube which serves as a weak thermal link. In order to evaluate the functionality of the device for use in a cryogenic radiometer, we measured the thermal resistance and thermal time constant of the system within the temperature range of 1.8 - 4.4 K. The measured thermal resistance and thermal time constant at 1.883 K were 2400 ± 500 (K/mW) and 24 ± 6 (s). This value for the thermal resistance should result in about an order-of-magnitude increase in radiometer sensitivity compared with the present ACR within LBIR. Although the sensitivity should increase by about an order-of-magnitude, the measured time constant is nearly unchanged with respect to previous ACRs within LBIR, due to the reduced dimensions of the receiver cavity. Finally, the thermal conductivity inferred from the measured thermal resistance and geometrical parameters was computed, with an average value of 0.015 (W/m-K), and compared with other measurements of polyimide from the literature.